At Polar Rose we simply started to put projects on Google Code. Some are well documented, others are mostly code dumps and need more attention. We use subversion internally and Maven for working with well defined (Java) components/libraries. So there is not much difference between working on code hosted in the public or private repositories.

The most difficult thing was actually not a technical thing but a mindset issue: To teach people in the teams how they can identify components that can be released as open source. And to actually do it.