I'm a big fan of Fulci and thought The Beyond was a killer flick! Zombie and House By The Cemetary are awesome. City Of The Living Dead has a couple of really great gorey moments and great atomosphere. Murder Rock is a pretty decent giallo style murder mystery (he toned down the violence for this one tho). I thought Possessed was average but a couple of trademark moments made it worth a watch but that flick ultimatley just gives you a headache.
The New York Ripper is hands down my favorite outta the stuff of his I've seen... but there's still a lot more movies of his I need to check out.
Chas Balun's book Beyond The Gates is worth a read if you can find a copy.
http://www.shockingimages.com/fulci/ <---- That site has a bunch of info on him.