Playing board games and card games online can be a lot of fun, no matter what style of games you like best. These are my favorite places to play board games and card games online.
BSW is a site that offers the ability to play designer (aka German) games online. Games available include Settlers of Catan, Carcassonne, Can't Stop, Liar's Dice (Bluff), Ra, Web of Power and many more. This link takes you directly to BSW, but many first-time players will want to read one or all of the assistance guides available in "Related Resources" below, since the site is mostly in German. (There are plenty of English-speaking players to be found, however.)
The thing that makes ItsYourTurn.com unique is that you only take one turn at a time -- so you and your opponents don't have to be online at the same time. Backgammon, Battleboats, Chess, Checkers, Go, Reversi and Sabotage (a Stratego-like game with some nice twists) are among the games available.
Among the offerings at GameTable Online are 10 Days in Africa, Backgammon, Checkers, Chess, Cosmic Wimpout, Kill Dr. Lucky, New England, Vampire, and more.
Chess, Othello, Pente, and many other abstract games can be played here. A good place for fans of abstract games.
Days of Wonder is a game publisher with versions of some of its most popular games, including Ticket to Ride, available online.