Here is some links to some of my most frequently visited sites.

Game Sites
Playok.com Play some of the world's strongest players in several different types of board games.
GoldToken This is the ACF supported website for checkers.
Yahoo! Always a large number of checker players here. Watch out for program users (cheaters) and short timed games.

Important Resources Websites
ACF checkers website Make sure you visit this site regularly, also check out the forum frequently on all sorts of things including new play, tournament information, general checker politics, and more. Also you can find information about tournaments, merchandise, and old time games.
English Draughts Association Excellent resource here with a ton of valuable information.
Wyllie Program One of the top competitive programs on the market today, visit here to find out about it!
Jim Loy's Website Problems, published play, and more
Al Lyman's website called Checkerworld Al always has had a lot of great information on his website. He also sells a program called straight checkers gold on here that is great for getting better.
Online Museum of Checkers History For the checker historian, all the facts are here!
Cake checker program This has became a popular program, partly because it is free, and it is very strong. They have many downloads for it including an 8 piece database.
Bob Newell's personal pages Problems, shots, openings, and more
World Championship Checkers website WCC the program and more
North Carolina Checker Association Maybe the best ran website of all. JR keeps plenty of pictures and information for everyone.