There have been lots of pictures and video of American swimmer Missy Franklin when she had braces (apparently up until only a few months ago).
American gymnast Jordyn Wieber's mother, Rita, is sporting clear braces top and bottom. She's done a ton of interviews with various sports channels and the braces are very obvious. She's also not a bad-looking lady! She mentions the braces on her blog, too.
Sorry, I don't have time to post links, but Google is your friend.