That a piece of hardware is LinuxCompatible is to say that either it adheres to a common standard that has already had a driver written for it, or that a driver has been written for it already.
Things that are LinuxCompatible include (you can't go wrong with these):
Things that are not LinuxCompatible include:
Phil's card reader/camera?
There are also things which do not work because the user lacks the required skill. This includes: GianPerrone's AC'97 onboard sound card. I am unashamadly a newbie to Linux sound.
One page links to LinuxCompatible: