Lots of things sell really well on eBay: Check out eBay Pulse for current hot favorites. Link hidden: Login to view
Finding what's going to work well for you on the other hand, is a different matter altogether.
The answer is Research, Research, Research.
Search the forum - there's been heaps of posts discussing this subject.
You might also want to take a look at these blog posts:
The Elusive eBay Product NicheLink hidden: Login to view
Good luck :)