Since the news broke, I have been curious to see which units were involved. I'm sure we will never know all the details but reports have been showing Navy Seals being involved. If Navy Seals are involved, then it's likely that the United States Naval Special Warfare Development Group did the deed since they are the Navy's counter terrorism unit. The linked article reports this as well.Lots of news stories have been posted on this event, but these guys are the hackers of the U.S. military.
Edit: Another play by play description.
http://blogs.abcnews.com/politicalpunch/2011/05/obama-gives-order-bin-laden-is-killed-white-house-time-line.html