PyMetis is a Python wrapper for the Metis graph partititioning software by George Karypis, Vipin Kumar and others. It includes version 5.0pre2 of Metis and wraps it using the Boost Python wrapper generator library. So far, it only wraps the most basic graph partitioning functionality (which is enough for my current use), but extending it in case you need more should be quite straightforward. Using PyMetis to partition your meshes is really easy—essentially all you need to pass into PyMetis is an adjacency list for the graph and the number of parts you would like.
Below is a sample partition of a toroidal finite element mesh, created using the included example