3GP is a common format for cell phones from what I've seen. I use SUPER to convert it; Apple's QuickTime should be able to play it, too--you'll need QuickTime Pro (non-free) to convert it.
I can't help in getting it off the phone; depending on how you're doing it, it will take awhile.
Their site is horrid, but here's the link to the SUPER site:
http://www.erightsoft.com/SUPER.html
It seems to work fine; every file I've thrown at it it has been able to convert. Except OGG Theora (I think, whatever the OGG video format is) - it was all rainbow striped. Oh well, it's still pretty good for a beta codec.
JBot