Eclipse has very sweet gdb integration, and is probably the best C/C++ IDE for Linux if people can get over the fact that it's written in Java and uses up gigs of ram.
Nothing on Linux beats the C++ parser that Eclipse has (I tried everything and it feels like programming in the stone age unless it knows how to interpret templates and go to def/go to usages works). Heck, even on Windows probably only Visual Studio beats it, thanks to being written in speedier native code and already supporting C++0x intellisense.
It's not as useful for C though since there's plenty of other IDEs that can do macro unfolding and if that's not even needed then just using your favorite text editor + cscope provides a fast way of traversing a call graph.
That being said C/C++ IDEs are still decades behind Java or C#. Where's our dozens of automated refactorings that other languages have?