Write about Red Data Tools, Ruby Numo, and SciRuby

Author: mrkn

index.md

@@ -4,3 +4,25 @@ RubyData aims to increase two populations of:
 
 1. Developers who write opensource data tools for Rubyists.
 2. Users who use opensource data tools with their products written in Ruby.
+
+## Development projects, organizations, and communities
+
+There are some projects, organizations, and communities that aim to make data tools for Ruby.
+
+### Red Data Tools
+
+Red Data Tools is a project that provides data processing tools for Ruby.
+
+Website: https://red-data-tools.github.io/
+
+### Ruby Numo
+
+Ruby Numo provides [numo-narray](https://github.com/ruby-numo/narray) and data analysis environment based on numo-narray.
+
+Website: https://github.com/ruby-numo
+
+### SciRuby
+
+SciRuby is a community of developers and users of data tools based on [nmatrix](http://sciruby.com/nmatrix/) library.
+
+Website: http://sciruby.com/