Widescreen UI's ?
 

Are there any custom UI's made specifically for 1680x1050?
If not..someone should get the ball rollin'

You don't really need a UI specifically for that resolution. You can simply resize and move individual windows as needed. I'm running FetishClassic on a widescreen without any problems what so ever. I just had to spend a few minutes setting it up the way I wanted and it's worked perfectly ever since.