Coming soon: A history of chess; Go Resources.
Blob Chess - This is my own creation. It's like standard chess, but with some restrictions - your pieces must move in a blob. Click the link to learn more!
Basic Chess Openings - This is a useful website for learning basic openings. It doesn't have every opening, but it contains the basics, and it includes basic traps you can try to set or avoid. Navigation in the site is based on clicking on a board. No sign-up necessary.
Chess Database - A very exhaustive database of games. This database contains all the famous games plus many not-so-famous games, including some correspondence games. Searching the database is mainly by moving pieces on a board to set up a position. A very useful tool. (Don't tell my chess correspondence friends!) No sign-up necessary.
Scheming Mind - Need some friends to play correspondence chess (chess by email, not real-time)? Here you can find many willing to play. A typical game can easily last a couple of months, but it's worth the challenge. Some of these players are pretty serious. This website also features variations on chess such as Fischer Random. Registration is required. You can access most of the site for free. This is by far the best website I've found for correspondence chess.
Chessgames.com - This is a great resource of general chess knowledge. It features a chess puzzle of the day. It contains news articles and player spotlights. There's also an extensive game database, but not as many games as the Chess Database mentioned above. The games in this database tend to be more "professional". The Opening Explorer is very useful, but you have to pay the membership to get full access.