Twitter love towards open source can help programmers across the globe to actively participate and grow with twitter projects and jobs. Right now twitter have listed few of the available projects done in Ruby, Scala, Java and C/C++ languages. Without just that, twitter also added up its job opportunities when we do great projects in the crowd. The engineering blog of twitter gives more info on the recent announcements on this.
All the projects are done via Github – Social Coding service. Another great platform to do a development in a collaborative way with bug fixing and many more features.