I've tried three usb sound adapters, all work out of the box on OSX ML 10.8.3:
"Syba SD-CM-UAUD71" - For me this one is the one I use and would recommend, imho it's the best of the three, it's inexpensive, sound quality is great and it has the volume/mic/mute control buttons are on the device, I've got a 4 plug usb hub on my desktop that I plug it into for quick access to the volume/mute controls. When not in use there is no noise or static on the headphones.
"SteelSeries Siberia" - Sound quality is equal to the Syba however this one is more expensive, the nice thing about this is the led lights are inside the device so no annoying flashing led lights like on the Syba (and most other usb sound adapters). I wouldn't recommend this one as there is noticeable noise & static you can hear in between songs and on Skype calls.
"Sabrent USB Sound Adapter" - For me, on my machine sound quality of the Sabrent was poor compared to the Syba or Siberia devices, this device would be ok for basic Skype use but I wouldn't recommend it for listening to music, was cheap enough and just I ended up just tossing it out.