Yahoo! has open source Mojito, a framework for creating reusable widgets incorporated in various web applications and executed either on the client or the server-side without code change.
The MacRuby team's busy working towards MacRuby 1.0, recently with the 0.10 release which adds XCode 4 support. Meanwhile, the first applications written using MacRuby have shown up in the Mac AppStore. Also: MacRuby seems to be part of the upcoming "Lion", Mac OS X 10.7.
Eclipse RAP (Rich Ajax Platform) in the real world is covered in this case study which looks at how CAS Software AG used RAP on a recent new product offering. Eclipse Equinox is also used by CAS and covered in the case study.