* [excon](https://github.com/excon/excon) - Usable, fast, simple Ruby HTTP 1.1. It works great as a general HTTP(s) client and is particularly well suited to usage in API clients.
* [Faraday](https://github.com/lostisland/faraday) - an HTTP client lib that provides a common interface over many adapters (such as Net::HTTP) and embraces the concept of Rack middleware when processing the request/response cycle.
* [Http Client](https://github.com/nahi/httpclient) - Gives something like the functionality of libwww-perl (LWP) in Ruby.
* [HTTP](https://github.com/httprb/http.rb) - The HTTP Gem: a simple Ruby DSL for making HTTP requests.
* [Http-2](https://github.com/igrigorik/http-2) - Pure Ruby implementation of HTTP/2 protocol
* [Patron](https://github.com/toland/patron) - Patron is a Ruby HTTP client library based on libcurl.
* [RESTClient](https://github.com/rest-client/rest-client) - Simple HTTP and REST client for Ruby, inspired by microframework syntax for specifying actions.
* [Savon](https://github.com/savonrb/savon) - Savon is a SOAP client for the Ruby programming language.
* [Sawyer](https://github.com/lostisland/sawyer) - Secret user agent of HTTP, built on top of Faraday.
* [Spyke](https://github.com/balvig/spyke) - Interact with REST services in an ActiveRecord-like manner.
* [Typhoeus](https://github.com/typhoeus/typhoeus) - Typhoeus wraps libcurl in order to make fast and reliable requests.
* [Mechanize](https://github.com/sparklemotion/mechanize) - Mechanize is a ruby library that makes automated web interaction easy.
* [Wombat](https://github.com/felipecsl/wombat) - Web scraper with an elegant DSL that parses structured data from web pages.
* [Anemone](https://github.com/chriskite/anemone) - web spider framework that can spider a domain and collect useful information about the pages it visits
* [HappyMapper](https://github.com/dam5s/happymapper) - allows you to parse XML data and convert it quickly and easily into ruby data structures.
* [HTML::Pipeline](https://github.com/jch/html-pipeline) - HTML processing filters and utilities.
* [Oga](https://github.com/YorickPeterse/oga) - An XML/HTML parser written in Ruby. Oga does not require system libraries such as libxml, making it easier and faster to install on various platforms.
* [Ox](https://github.com/ohler55/ox) - A fast XML parser and Object marshaller.
* [ROXML](https://github.com/Empact/roxml) - Custom mapping and bidirectional marshalling between Ruby and XML using annotation-style class methods, via Nokogiri or LibXML.
* [diffy](https://github.com/samg/diffy) - a convenient way to generate a diff from two strings or files
* Phone number
* [GlobalPhone](https://github.com/sstephenson/global_phone) - Parse, validate, and format phone numbers in Ruby using Google's libphonenumber database.
* Country names
* [i18n_data](https://github.com/grosser/i18n_data) - country/language names and 2-letter-code pairs, in 85 languages, for country/language i18n.
* [normalize_country](https://github.com/sshaw/normalize_country) - Convert country names and codes to a standard, includes a conversion program for XMLs, CSVs and DBs.
* Date & time
* [Chronic](https://github.com/mojombo/chronic) - A natural language date/time parser written in pure Ruby.
* [yymmdd](https://github.com/sshaw/yymmdd) - Tiny DSL for idiomatic date parsing and formatting.
* User agent
* [Device Detector](https://github.com/podigee/device_detector) - A precise and fast user agent parser and device detector, backed by the largest and most up-to-date user agent database.
* General parser
* [Parslet](http://kschiess.github.io/parslet/) - A small Ruby library for constructing parsers in the PEG (Parsing Expression Grammar) fashion.
* [markup](https://github.com/github/markup) — GitHub library to convert mardown, rst, creole, etc into HTML
* Office
* [Yomu](https://github.com/Erol) - Read text and metadata from files and documents (.doc, .docx, .pages, .odt, .rtf, .pdf)
* [spreadsheet](https://github.com/zdavatz/spreadsheet) - The Spreadsheet Library is designed to read and write Spreadsheet Documents.
* [roo](https://github.com/Empact/roo) - Roo implements read access for all spreadsheet types and read/write access for Google spreadsheets.
* [google-spreadsheet-ruby](https://github.com/gimite/google-spreadsheet-ruby) - This is a library to read/write Google Spreadsheet.
* [rubyXL](https://github.com/weshatheleopard/rubyXL) - rubyXL is a gem which allows the parsing, creation, and manipulation of Microsoft Excel (.xlsx/.xlsm) Documents
* [remote_table](https://github.com/seamusabshere/remote_table) - Open local or remote XLSX, XLS, ODS, CSV (comma separated), TSV (tab separated), other delimited, fixed-width files, and Google Docs.
* [sheets](https://github.com/bspaulding/Sheets) - Work with spreadsheets easily in a native ruby format.
* [workbook](https://github.com/murb/workbook) - Workbook contains workbooks, as in a table, contains rows, contains cells, reads/writes excel, ods and csv and tab separated files...
* [oxcelix](https://github.com/gbiczo/oxcelix) - A fast Excel 2007/2010 (.xlsx) file parser that returns a collection of Matrix objects
* [wrap_excel](https://github.com/tomiacannondale/wrap_excel) - WrapExcel is to wrap the win32ole, and easy to use Excel operations with ruby. Detailed description please see the README.
* libpcap
[PacketFul](https://github.com/packetfu/packetfu) - A library for reading and writing packets to an interface or to a libpcap-formatted file.
* JSON
* [JsonCompare](https://github.com/a2design-company/json-compare) - Returns the difference between two JSON files
* [JSON](https://github.com/flori/json) — includes pure Ruby and C implementation for JSON.
* [JSON::Stream](https://github.com/dgraham/json-stream) — a streaming JSON parser that generates SAX-like events.
* [YAJL](https://github.com/brianmario/yajl-ruby) — a streaming JSON parsing and encoding library for Ruby (C bindings to YAJL).
* [OJ](https://github.com/ohler55/oj) — Optimized JSON, as the name implies, was written to provide speed optimized JSON handling. So far it has achieved that, and is about 2 times faster than any other Ruby JSON parser, and 3 or more times faster at serializing JSON.
* Markdown
* [kramdown](https://github.com/gettalong/kramdown) - Kramdown is yet-another-markdown-parser but fast, pure Ruby, using a strict syntax definition and supporting several common extensions.
* [Maruku](https://github.com/bhollis/maruku) - A pure-Ruby Markdown-superset interpreter.
* [Redcarpet](https://github.com/vmg/redcarpet) - A fast, safe and extensible Markdown to (X)HTML parser.
* ATOM/RSS
* [Feed normalizer](https://github.com/aasmith/feed-normalizer) - Extensible Ruby wrapper for Atom and RSS parsers.
* [Feedjira](https://github.com/feedjira/feedjira) - A feed fetching and parsing library.
* [Ratom](https://github.com/seangeo/ratom) - A fast, libxml based, Ruby Atom library.
* [Simple rss](https://github.com/cardmagic/simple-rss) - A simple, flexible, extensible, and liberal RSS and Atom reader.
* BSON
* [BSON](https://github.com/mongodb/bson-ruby) — Ruby implementation of the BSON Specification (2.0.0+), http://bsonspec.org
* MessagePack
* [MessagePack](https://github.com/msgpack/msgpack-ruby) — an efficient binary serialization format. It lets you exchange data among multiple languages like JSON but it's faster and smaller. For example, small integers (like flags or error code) are encoded into a single byte, and typical short strings only require an extra byte in addition to the strings themselves. See http://msgpack.org
* Protobuf
* [Protobuf](https://github.com/localshred/protobuf) — Ruby implementation for Protocol Buffers.
* [Pragmatic Segmenter](https://github.com/diasks2/pragmatic_segmenter) - Pragmatic Segmenter is a rule-based sentence boundary detection gem that works out-of-the-box across many languages.
* [Text](https://github.com/threedaymonk/text) - A collection of text algorithms including Levenshtein distance, Metaphone, Soundex 2, Porter stemming & White similarity.
* [Parallel](https://github.com/grosser/parallel) - Run any code in parallel Processes (> use all CPUs) or Threads (> speedup blocking operations).
* [Concurrent Ruby](https://github.com/ruby-concurrency/concurrent-ruby) - Modern concurrency tools including agents, futures, promises, thread pools, supervisors, and more.
* [childprocess](https://github.com/jarib/childprocess) - Cross-platform ruby library for managing child processes.
* [forkoff](https://github.com/ahoward/forkoff) - brain-dead simple parallel processing for ruby.
* [posix-spawn](https://github.com/rtomayko/posix-spawn) - Fast Process::spawn for Rubys >= 1.8.7 based on the posix_spawn() system interfaces.
* [Sidekiq](http://sidekiq.org) - A full-featured background processing framework for Ruby. It aims to be simple to integrate with any modern Rails application and much higher performance than other existing solutions.
* [Que](https://github.com/chanks/que) - A Ruby job queue that uses PostgreSQL's advisory locks for speed and reliability.
* [Shoryuken](https://github.com/phstc/shoryuken) - A super efficient AWS SQS thread based message processor for Ruby.
* [Sucker Punch](https://github.com/brandonhilkert/sucker_punch) - A single process background processing library using Celluloid. Aimed to be Sidekiq's little brother.
* [Metainspector](https://github.com/jaimeiniesta/metainspector) - scrapes a given URL, and returns its title, meta description, meta keywords, an array with all the links, all the images in it, etc
* [LinkThumbnailer](https://github.com/gottfrois/link_thumbnailer) - Ruby gem that generates thumbnail images and videos from a given URL. Much like popular social website with link preview.
* [geocoder](https://github.com/alexreisner/geocoder) - A complete geocoding solution for Ruby. With Rails it adds geocoding (by street or IP address), reverse geocoding (find street address based on given coordinates), and distance queries.
* [geoip](https://github.com/cjheath/geoip) - Searches a GeoIP database for a given host or IP address, and returns information about the country where the IP address is allocated, and the city, ISP and other information.
