Yahoo used to have a scrabble applet (java-based, very simple graphic but completely sufficient and it would save games ao that you could continue even months after an interruption). Last time I played was about 8 years ago IIRC. Must check occasionally if that app is still there.
Well, there's Starcraft 2, Team Fortress 2, etc., but since we're talking about casual games here ... I play Landgrab, which is an online version of Risk with new maps, support for more players (100+), teams, tournaments, etc. Most game settings give you 24-72 hours to take your turns, so you just log in a couple of times a day to take your turns. It's also especially fun when you get a long running game going (I'm hitting the 3rd year anniversary for a game next month) which makes the wars feel really epic. There's nothing like a 9 month cold war suddenly turning hot. I usually have about 20-30 games going at once. Also, I'm forced by family obligation to play Words With Friends.
I play Tetris online a lot. I've always been a huge Tetris fan, and I still have my original 1988 Gameboy Tetris cartridge! I beat Super Mario Bros 3 when I was a kid, but I don't play any other computer or video games. Starting in the mid 90s game graphics, especially first-person, started giving me severe motion sickness. The first time it happened was watching my mom play Journeyman. Just a few seconds of a modern game is enough to make me dizzy and nauseated -- which is ironic, as I've never gotten motion sickness from actual motion. I still break out my old gameboy on occasion, and I beat Super Mario 3 for a second time about 6 years ago when I was really depressed for a month.
I've played video, computer, and board games all my life--from the original Nintendo ES Super Mario Brothers to Scrabble to PC games like Jeopardy and Wheel of Fortune to Millionaire to MMOs and The Sims 1, 2, and 3. But I've outgrown most of them. I still play Angry Birds occasionally. I have a PS3 that I use mostly for watching movies and playing Super Streetfighter 4.
Link, please!!! =) I'm an addict, too. Got an old Win98 diskette version which amazingly still runs on XP but I haven't dared yet to try it on Vista.
^I play Tetris Battle through Facebook. It's a different beast from original Tetris (which I still play on my gameboy), but the two minute games are perfect for in between posting, reading, or while watching TV. It can get a little frustrating, and it's clearly rigged, but it's still fun, and not too buggy for a Facebook game.
IC. I never use facebook. They sell userdata and you get spammed like crazy. Hmm, maybe I can find a Tetris version that runs on Vista. And if I can't, I'll simply write one for my other computer that runs Linux (one of the big advantages of open source software!)
^I actually use a dummy account specifically for Facebook gaming. It spams a dummy yahoo email address that I haven't visited in 2 years, there's no user data to sell, and I can play all I want. Facebook can only sell data you give them.