The Python Standard Library is an extensive library. Most of the time, this library will have what you are looking for. This is referred to as the 'batteries included' philosophy of Python. I highly recommend that you go through the Python Standard Documentation before you proceed to start writing large Python programs.

Python.org - the official homepage of the Python programming language. You will find the latest versions of the Python language and interpreter here. There are also various mailing lists where active discussions on various aspects of Python take place.

comp.lang.python is the usenet newsgroup where discussion about this language takes place. You can post your doubts and queries to this newsgroup. You can access this online using Google Groups or join the mailing list which is just a mirror of the newsgroup.

Python Cookbook is an extremely valuable collection of recipes or tips on how to solve certain kinds of problems using Python. This is a must-read for every Python user.

Charming Python is an excellent series of Python-related articles by David Mertz.

Dive Into Python is a very good book for experienced Python programmers. If you have thoroughly read the current book you are reading, then I would highly recommend that you read 'Dive Into Python' next. It covers a range of topics including XML Processing, Unit Testing and Functional Programming.

Jython is an implementation of the Python interpreter in the Java language. This means that you can write programs in Python and use the Java libraries as well! Jython is a stable and mature software. If you are a Java programmer as well, I highly recommend that you give Jython a try.

IronPython is an implementation of the Python interpreter in C# language and can run on the .NET / Mono / DotGNU platform. This means that you can write programs in Python and use the .NET Libraries and other libraries provided by these 3 platforms as well! IronPython is still pre-alpha software and is suitable only for experimenting as of now. Jim Hugunin, who wrote IronPython has joined Microsoft and will be working towards a full version of IronPython in future.

Lython is a Lisp frontend to the Python language. It is similar to Common Lisp and compiles directly to Python bytecode which means that it will interoperate with our usual Python code.

There are many many more resources on Python. Interesting ones are Daily Python-URL! which keeps you up to date on the latest Python happenings, Vaults of Parnassus, ONLamp.com Python DevCenter, dirtSimple.org, Python Notes and many many more.