A PyCon 2011 talk called "Dude, Where's My Ram?" by David Malcolm presented gdb-heap, a debugging tool that takes advantage of GDB v7's new Python API. The nice part of this tool is that it allows you to inspect your heap core dumps and Python processes without having to add additional instrumentation beforehand.
The code released was originally designed and implemented for Fedora 13 and Fedora 14 back in 2011, but I've managed to figure out how to get it working on Ubuntu v12.04. The GitHub repo is located here: https://github.com/rogerhu/gdb-heap
The code in its current form did not appear to have updates to support glibc v2.15's multiple allocation arenas (see http://stackoverflow.com/questions/10706466/how-does-malloc-work-in-a-multithreaded-environment), so I've started to try to add more support in this GitHub repo. The libheap project is a similar implementation but incorporates multiple arenas, but doesn't carry some of the special logic heuristics and query parser for searching for certain heap sizes.