I'd like to enumerate all the new stuff that went into the second edition of "Invent Your Own Computer Games with Python".
First, the book itself features four new chapters that covers Pygame, a game library for Pygame that makes it easy to create programs with GUIs that display graphics, play sounds, and accept mouse input.
Second, the 2nd edition covers the newer Python 3 version.
Third, the new website (http://inventwithpython.com) has been updated with several new features. The online diff tool allows you to compare your code with the books, so you can tell immediately where you've made typos. The Python interpreter's error messages can sometimes be very cryptic, especially to the beginner. Finding the source of these error messages can be tedious without the diff tool.
The website has a videos section, where the videos on the book's YouTube page at http://www.youtube.com/user/inventwithpython. (Currently, there is only a video accompanying the Reversi chapter. However, a screencast tutorial that follows along with the book is planned.)
The web site also has an extra content section, where additional programs and chapters that were cut from the book are placed.
These sections will be expanded in the future as their contents are organized.