While I didn't discover it until the latter half of 2009, I'd have to say eventlet is the coolest Python library I discovered in 2009. After leaving Slide, where I learned the joys of coroutines (a concept previously foreign to me) I briefly contemplated using greenlet to write a coroutines library similar to what is used at Slide. Fortunately I stumbled across eventlet in time, which shares common ancestry with Slide's proprietary library.
I'm not sure I really learned any new techniques over the past year, I started writing a lot more tests this past year but my habits don't quite qualify as Test Driven Development just yet. As far as Python goes, I've been introduced to the Python C API over the past year (written two entire modules in C PyECC and py-yajl) and while I wouldn't exactly call implementing Python modules in C a "technique" it's certainly a departure from regular Python (
Py_XDECREF I'm looking at you)
Regular readers of my blog can likely guess which open source project I contributed to most in 2009, Cheetah, of which I've become the maintainer. I also authored a number of new Python projects in 2009: PyECC a module implementing Elliptical Curve Cryptography (built on top of seccure), py-yajl a module utilizing yajl for fast JSON encoding/decoding, IronWatin an IronPython-based module for writing WatiN tests in Python (supporting screengrabs as well), PILServ an eventlet-based server to do server-side image transformations with PIL, TweepyDeck a PyGTK+ based Twitter client and MicroMVC a teeny-tiny MVC styled framework for Python and WSGI built on eventlet and Cheetah.
The Python reddit was probably the most read Python-related "blog" I read in 2009, it generally supercedes the Python Planet with regards to content but also includes discussions as well as package release posts.