Are you a friend of Star Trek on face book? They started a poll for what would be Kirk's ringtone. The results are quite amusing, it's worth a look.
It got me thinking, what would be the ring tone of other characters from Star Trek?
Geordi La Forge might have "Harder Better Faster Stronger" by Daft Punk.
Wesley Crusher might have some totally nerdy ring tone, like the Final Fantasy battle end jingle (with the Mario power up for sound for a message alert)
Tom Paris might have "Flash" or "Princes of the Universe" by Queen (what with his love of "retro" sci-fi) or maybe something by Bruce Springsteen or John Mellencamp, you know a song about a car. For Belana he might have a special ring tone, maybe a Klingon Opera about a woman who decapitates her enemies in the name of love (odds are there are at least 5 Klingon operas just like that).