I see many people with pictures of their XBox Live avatars on their websites, and I wondered how it was done.
Turns out, its extremely simple.
Type http://avatar.xboxlive.com/avatar/<XBox Live ID>/avatar-body.png into your browser, substituting the <XBox Live ID> for your gamertag, and you’ll have a PNG of your avatar.
Like I said, simple!
BTW: Here is my current avatar: