Pricing for Xbox LIVE Gold is as follows: $7.99/month OR $19.99 for 3 months OR $49.99/year. You can purchase any of these plans via the Xbox LIVE "Dashboard" (pages are now called "blades") or you can purchase in-store cards and then enter the info into your 360 (that way, you don't need a credit card to sign-up).
Going further, Microsoft has two bundles which include Xbox LIVE Gold service and a headset. These bundles are named, "Xbox Live Premium Gold Packs". For $39.99 you get a 3 month subscription, headset, access to "Xbox LIVE Arcade" game, Joust, a $10 coupon for any Xbox 360 game, and 100 Marketplace points. For $69.99 you get a year subscription, headset, access to "Xbox LIVE Arcade" game, Bankshot Billiards, a $20 coupon for any Xbox 360 game, and 200 Marketplace points.
If you currently have Xbox LIVE your service will automatically be transferred to your Xbox 360 at the Gold Service level. However, I'm not sure if your current headset will work with the new controller (I would hope it does), so many of us may be stuck buying a subscription bundle unless you can buy a headset separately or if, indeed, the old headset works. I looked around for a while today to see if I could find the answer to this headset question, but didn't find anything. I'll update you if I do.
Anyway, along with the pricing announcement came some fun stats about the current Xbox LIVE service. Houston is the most connected city (aren't they also the fattest city? Hmm?) with London coming in third. There are a total of 2 million Xbox LIVE subscribers. Online games are expected to reach up to $3.8 billion in revenue by 2009. Xbox Live gamers have accrued more than 1,378,074,883 hours on the service, which is 57,419,787 days or 157,314 years.