Well its not FOSS but Rational supplies a complete tool chain (except for the compilers!),
You get IDEs, Class diagrams, use cases, requirements tracking, test tools, problem logging tools which integrate well all for a few thousand (or hundreds of) dollars.
None (aprt from the modeling tools) is best of breed, but, they are all pretty good and integrate well with each other.
Disclaimer:-
My "toolset" of choice is vim,make, ffffd, gmail and a moleskin notebook for modeling.
