If it's new stuff I would definetly list them on eBay. You'll get rid of them faster than posting them on any classifieds website and you'll likely get more for them too. You can't list used cloth diapers and covers on eBay but new is fine and still sells well.

Other than that I would say Diaperswappers as well. It's a bit of a pain at first because you have to have a certain number of posts to list with pictures (and pictures really are a must in my opinion) but it really is the place you'll get the most exposure to other cloth diaperers. There's lots of Canadians there too so you won't necessarily have to ship to the US (not that it's really much more trouble).

Places like Kijiji will work but you'll either have to put them at a pretty low price or be patient till you find someone willing to pay what they're worth.

Karen.