I was unable to get the links poster earlier to work, so I may be repeating what others have said but the best tool I have found is a 'TIRE BEAD JACK'. I don't have a picture but it cost me about ten dollars at the lbs that ordered it for me. It is for remounting a tire but doesn't help with getting a tire off the rim. Also, I put some vaseline on the last part of the rim that I'm trying to push the bite back onto.
As for getting the tire off, I would suggest a longer tire lever than the smaller ones people usually carry. The picture posted by sour01 seems to be a longet unit.
Just Google 'Tire Bead Jack'. Ten dollars and about three ounces.