http://www.gravestonephotos.com/index.php

 I found details of an ancestor's gravestone with information on it that expanded my knowledge of that person. Well worth a visit and going back from time to time as more graveyards are being photographed and recorded.  I have also been inspired to volunteer to document the graveyard where my parents are buried, making a start yesterday photographing the first batch of gravestones and indexing them this morning.

Almost forgot to mention the most important point! It is free to use.