GDB Python integration
The GDB Python integration is really awesome. But whenever I want to point people at it I never know what a good overview is to link them to. So I created a little PythonGdbTutorial page on the GDB wiki that has just a one sentence summary and links to all the articles Tom Tromey wrote about the cool stuff that is now possible. Like implementing new gdb commands, convenience functions, filtering backtraces, pretty printers, scripting gdb itself and even writing a whole new GUI, all in python of course.
Update: Phil Muldoon pointed out that the online GDB manual is also completely up to date now. See the GDB Python chapter.