GCC version 4 has been out for several years now, and anyone still using version 3 is probably living in a box ... or just has very, very specific requirements for their build environment. Nevertheless, IBM Developerworks are running an article detailing what's new in GCC 4.
Josef Nygrin has written a fantastic guide to Doxygen, which is a documentation system for C, C++, Objective-C, Python, Java and a number of other languages.
The LLVM Developer group have announced the release of version 2.2 of LLVM, an open source compiler infrastructure, which supports compilation of C, C++, Fortran, Objective C and Ada programs.
If you'd like to try it out before downloading, they even have an online demo available.