The new Xbox.com is up and running with Xbox 360 features. You can now include your Gamer Card in web pages, blogs, etc. by including the following fragment:

<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>

Which will result in this:

See this for more information.