The new Xbox Live Gold 12-month Starter Kits that were released with the 360 come with a coupon for $20 of a 360 game. I don't know the details of the coupon though. I don't know if it's like a rebate that you can redeem for a game you already got, or if you have to buy another new game, and how long it's valid, etc.
The starter kit is $70, and in addition to the coupon, it comes with a headset, Bankshot Billiards Live Arcade game, and 200 MS points (which is not very much at all). If you bought the Premium 360 package, then the headset probably isn't very useful. Very few games allow you to have two players playing online with one Xbox, hence the need for two headsets. The only game I can think of that allows this is Halo 2.
A normal 12-month subscription to Xbox Live (without the starter kit) is $50. So, if you use the coupon from the starter kit, it's like you're getting the headset, the billiards game, and the 200 points for free. It would really only be a good deal if you don't have a headset. Otherwise, it's not that great.
If you want to hold off on Xbox Live, every now and then I see retailers like Best Buy offer a discount on the subscription when you buy a game at the same time. Like, I sometimes see, "Buy [X] game and a 12-month Xbox Live card and save $10" or something.
You really should get Xbox Live anyways. $50 a year works out to $4.17 a month, which is a really good deal for unlimited online gaming imo.