Jeff Jenkins has graciously (and apparently posthumously since I had added his site to my links graveyard a while back) released a second version of his XNA 360 Controller button graphics for use in your XNA created games. What's that you say, why did I say "second", well that's because many, many moons ago he released his first XNA Button pack!
The only complaint that I have with these button packs is that, well, he's a much better artist than I am, so when I stick them into my games it just reminds me of how far I have to go before my mad skillz (yeah, I used a "z") get to that point. But other than damaging my pride, these are a tremendous resource for adding that polish and shine to any game.
I've also resurrected Jeff's site over at 360Prophecy from my links graveyard and added him as my very first link in my "Game Assets" link section.
Enjoy!