We recommend Ruby 1.8.7 for use with Rails. Ruby 1.8.6, 1.8.5, 1.8.4 and 1.8.2 are still usable too, but version 1.8.3 is not. Source: Compile it yourself Windows installer: Ruby, popular extensions, editor OS X 10.4: Ships with broken Ruby, follow this guide OS X 10.5: Included with developer tools (then do "gem update rails") RubyGems is the standard Ruby package manager. It's sim