The latest version of FXRuby is always available from the RubyForge project page. The RubyForge releases should always have accompanying release notes describing the changes for that release. A cumulative ChangeLog file is also included in the FXRuby source code distribution. Note that any FXRuby 1.6.x release should be compatible with any FOX 1.6.x release, but won’t be compatible with earlier (or later) versions of FOX.
The FXRuby source code is distributed as a gzipped tar archive, and is available for download from the RubyForge project page.
Binaries for Unix/Linux
Precompiled binaries for FOX, FXScintilla and FXRuby are available for various Unix/Linux platforms, but not in any centralized way.
Both the FOX Community Wiki site and the main FOX web site list a number of independent sources for package downloads for various Linux distributions, but many of these are for older FOX releases. You may have better luck using a RPM search engine like rpmfind.net to find the most recent packages for your distribution.
Binaries for Microsoft Windows
Windows installers for FXRuby are available for download from the RubyForge project page. The FOX and FXScintilla libraries are built into the Windows installers for FXRuby, and you should not need to download and install those packages separately. These binaries are also compatible with the standard Ruby installer for Windows that are available for download from RubyForge.
Note that the precompiled binaries for Windows are built with OpenGL support, and thus depend on the OpenGL runtime libraries (opengl32.dll and glu32.dll). These libraries were not included with Windows 95 (earlier than OSR2), so if you’re using Ruby and FXRuby on a Windows 95 machine, you may need to download the OpenGL runtime libraries. You must have these libraries installed even if you don’t plan to do anything OpenGL-related with FXRuby.