Also see All About Peer-To-Peer Architecture in Webopedia's "Did You Know...?" section.

Peer-to-Peer Communications Inc.
Features technical titles on programming, operating systems, hardware, software, and the Internet. Includes non-fiction books about the industry.

The Power of Peer-to-Peer
Companies are using the technology to get more from their systems.

Yahoo's Peer-to-Peer Page
Yahoo's directory of peer-to-peer file sharing resources.

What Network Do You Need?
An overview of the different types of networks possibilities, from peer-to-pear to client/server, and what kind of products you need to run them.