There are quite a few useful websites on Paris cemeteries, with a surprising number in English. The ones I have found to be most helpful are:

Cemeteries of France (with special focus on Paris, by Philippe Landru, French only)
Les Invalides (Wikipedia)
Pantheon
Friends of Pere-Lachaise (French)
Pere-Lachaise (Wikipedia)
Pere-Lachaise (interactive map)
Pere-Lachaise Crematorium (French)
Pere-Lachaise Sculpture
Saint-Denis (official site)
Saint-Denis (Wikipedia)
Saint-Denis list of royal burials (Find-A-Grave)

Remember that the internet is a dynamic environment; sites come and go, domain names change and links break. If you find a problem with any of the links above or believe you are being spammed as a result of clicking through please let me know.

Or if you would like to recommend a website, just drop me a note. Thanks!

(Photo below: "Dalida" in division 18, Montmartre.)