It depends on what you want to do with Python.
For web development, many swear by Django. I haven't used it extensively, but I know that the documentation on the site is good and there are a number of books that cover the topic extensively (e.g. Professional Python Frameworks). Also, I've heard good things here and there about CherryPy, Turbogears, and Pylons as well, you can look at those to see if they suit you.
For GUI development, there's a bit of debate. There are several books out there for PyQt, and there's a loyal following for PyGTK as well. I personally use Tkinter, but I find the documentation for Tkinter is good for basic stuff, but is certainly not comprehensive or up-to-date.
For internet programming (not web applications, but more along the lines of protocols--FTP, email, etc.), the Python library reference (note: this is a link to the 2.7 docs) provides you with most of what you need to know to get started.
For anything else, there's pretty much everything you'd want in the Python library.