ExpertFootball.com
It's a great place to learn about the history of the sport, the most heated derbies, top players, and it also has links to other good sites worth checking out.
WeCallItSoccer.com
Home of the "Free Beer Movement" in promoting MLS. Entertaining and insightful at the same time. Also has links to other sites worth checking out.
Just a few websites off the top of my head.