How do you manage shared software in a large project?

I’m working on a project too large to live in the same Visual Studio / Eclipse / NetBeans project, and we have a “common software” team responsible for developing and maintaining the software libraries used by other teams.

I struggle for how to manage the development and change of general software. When signatures and method classes change, keep old versions and mark them obsolete? The current plan is to distribute a new assembly of shared libraries every two weeks.