UPDATE November, 2012:  The new SatoshiDICE site is launched!  

UPDATE AUG 19, 2012: SatoshiDICE has released paying shares
https://bitcointalk.org/index.php?topic=101902.0

Hi all,

SatoshiDice.com is the world's most popular Bitcoin betting site. Over 1,000,000 BTC has been won and over 1,500,000 individual bets placed (as of November 2012). Bet options are available with up to 64,000x multiples and a house edge of only 1.9% (and bet results are mathematically provably fair). To play, you just send coins to any of the listed addresses based on the odds you want.

To see how easy it is, try sending 0.01 btc to 1dice9wcMu5hLF4g81u8nioL5mmSHTApw
(That address gives you a 73% chance of winning)

Payout is sent almost immediately (doesn't need to wait for confirmation). Super fast, easy, and fun Remember to do this only from wallets that let you receive coins from the address you sent them from (standard wallet, or blockchain.info wallet, both work great - if unsure about your wallet, test with a tiny amount and if you never get a payment back, then your wallet is incompatible).

Many other bet odds available at the site.

Enjoy SatoshiDICE!