This book has covered a lot of ground. I hope you have learned enough to develop better games. The following resources should help you out a little—I've included all the links, books, source code, and games that were mentioned throughout the book.
Here's a list of many important links from the book:
XNA Creators Club from Microsoft is where all the XNA Game Studio forums are located. They are the most active XNA forums you will find on the Internet. You can also download the latest XNA version here, check out tutorials and samples, read the FAQ, and see what's new.
Bookmark this XNA Team blog to stay up-to-date with the latest news from the XNA team.
This is the official website of the author. You can find more games here, as well as Rocket Commander XNA, the XNA Shooter, and the Racing Game from this book. All of the documentation and video tutorials that I made for the games are also here. Additionally, I suggest checking out the Rocket Commander Video Tutorials, which were pretty popular on Coding4Fun.
This is the official website for Rocket Commander, which was released at the beginning of 2006. It was written for Managed DirectX originally. A new version running completely on XNA to support the Xbox 360 was released at the end of 2006.