Personally I'm using a ROKR E2. It runs on Linux/Java, has a USB 2.0 high speed port (the others have USB 1 which is really slow). The E2 comes with a 1.3MP camera, A2DP (stereo) Bluetooth (music and file transfer supported), MP3 player (not limited to 100 songs like iTunes), decent battery life, medium RF performance (not nearly as good as my old ROKR E1), and SD memory card slot (I have a 2GB card that holds tons of songs). You can find new, unlocked units for ~$250USD if you look.
If you are getting the L7 or V3i free with service, I'd go with the V3i. It has a nicer camera.
Tango Uniform.