I'm using the very common BELKIN F5D7050 usb 801.11G ADAPTER
version 'V4000uk' using a Realtek driver included in Ubuntu Feisty &
Gutsy. It works transparently. I have another ver 2000UK which does
not use the same driver and is not Realtek so I have not experimented
with it. (Let sleeping dogs lie!)

I also use a much older F5d6050 8011b on Mint and it also works out of
the box on Mint 3. You'll get one of these for a song on ebay.