ziggyware.com — A networking tutorial with a game making perspective. Has 5 parts. (not too long) It has bits on how to implement it, and has a basic implementation example of TCP. It also has a section about Security and how what information should be sent from server to client to keep hackers at bay. read more...
onlinegametechniques.blogspot.com — Darrin West discusses the subject/observer pattern in relation to fast and slow moving entities in online games. read more...
gamasutra.com — In this Intel sponsored feature, former Insomniac and current Intel staffer Orion Granatir introduces threading by comparing it to networking in games. read more...
blogs.msdn.com — Dan Waters shares with us his latest installment in his Zune series: Building a networked Zune game. The potential is huge - imagine a group of six people playing Monopoly wirelessly on their Zunes, or some other board or card game. (That's next for me!) But for right now, the goal is to understand the fundamentals. That means going over peer-to-peer architecture and sending network packets. read more...
blogs.msdn.com — Shawn explains the types of network topologies and explains why he favors hybrids. Very nice article in showing examples of different types he would use for different types of games. read more...
nyxtom.vox.com — Thomas Holloway has posted an article on TCP based networking in XNA and how his API works. read more...
gamedev.net — In light of XNA's new Networking Support, this article (from 2001) clearly describes some of the issues you'll encounter with lag, and presents a simple way of dealing with them. read more...