In my opinion, this is the best manual to have if you want to do most of your XT500 maintenance yourself.  The text and pictures are easier to follow and much clearer than the Clymer manual.  This manual is a must have!  (Check your local library for this one, they may just have it!)

This manual has a great section on White Brothers performance enhancements, but is harder to follow than the Haynes manual.  It seems like it has been written more for the experienced mechanic and omits many details that the beginner needs, especially when trying to remove parts!

This is a good place to start for basic XT maintenance, but I highly recommend obtaining at least one of the above manuals for more thorough servicing information.