In response to Tarek's meme
Sphinx. Sphinx is really super. It makes writing and publishing technical documentation less painful by an order of magnitude than it used to be. I'm actually not sure this wasn't a 2008 discovery, but I really started using it "in anger" on my own projects in 2009.
Testing using statement coverage (via Ned Batchelder's coverage). Maintaining 100% statement coverage gives me a lot more confidence about refactoring old code.
Repoze (including BFG). I wrote the lion's share of BFG and contributed to various other Repoze-related pieces of software. I also did a good bit of work on Karl (a collaboration system based on BFG and other Repoze software). I also did some work on Formish/Schemaish, Pylons/Routes, WebOb, and Sphinx.
Reddit's Python section, and the blog entries tossed at me by Planet Python.
No idea. I just take it as it comes.