Kroobe offers quality filtered listings that can be easily reviewed and flagged. It connects to Facebook , Twitter and LinkedIn for logins and sharing ( though sharing is optional). Users can contact one another via a messaging system that keeps email private.
Kroobe is a dramatic overhaul of the online classified concept.

Everyone knows them. Simple but pretty spammy these days. Many of the responses are people trying to cheat you.

Seems like the closest competitor to Craigslist. Clean Web 2.0 ish look. Has Facebook connect and also seems to power the Facebook classifieds marketplace.

eBay's own local classifieds service even though they own a big chunk of craigslist.