You may have noticed that my Xbox Gamer Card showed up on the right hand side of the site this week. I found
<iframe src="http://gamercard.xbox.com/REPLACE-THIS-WITH-YOUR-GAMERTAG.card" scrolling="no" frameBorder="0" height="140" width="204">Put your gamertag here too.</iframe>
If you've got a space in your gamer tag, you'll need to replace the space with %20.
So if you were Major Nelson, yours would look like:
<iframe src="http://gamercard.xbox.com/major%20nelson.card" scrolling="no" frameBorder="0" height="140" width="204">Put your gamertag here too.</iframe>
Official details are here:
http://www.xbox.com/en-US/MyXbox/embedgamercard.htm
And if you're curious how it's possible that I've only got 20 points on my gamer card ... 
I actually have another account I've had forever (tallguy), but there was a bit of a mixup when trying to get the account changed over. Net-net, I ended up with two accounts, and can't transfer anything (points, rep, or score) from the original account to this one. Sounds to me like a good excuse to play alot of Gears of War when I get home this weekend.