http://www.microsoft.com/presspass/press/2005/jan05/01-20XboxLive04BenchmarkPR.asp

Some other interesting stats from the press release:

• There are now more than 200 Xbox Live -enabled titles, making it the richest library of online console games available today
• Halo 2 has sold more than 6.4 million copies worldwide.
• The Xbox Live community has logged a record-breaking 91 million hours playing "Halo 2" since the title's launch.
• There have been close to 61 million logged sessions for Halo 2, with an average session lasting nearly 92 minutes.

More stats (not from the article)

• XBox Live Subscribers were broke 1 million on July 15th. That means that there has been over 400,000 new subscribers in 6 months.
• Doing a little arithmetic, we can see that 6.4 million copies of Halo 2 minus 1.4 million XBox subscribers means that there are 5 million people out there who own Halo 2, but aren't playing it on Live. C'mon folks, what are you waiting for?!