I've tried many parking sites, including Sedo and Afternic. I've had the best experience (and consistent or growing revenues) with DomainSponsor.com, iMonetize.com and TrafficClub.com. Be sure to leave your domains parked in one place for at least 30-60 days to get an accurate picture of how you can expect them to do there. If your CTR, RPC or RPM aren't acceptable to you after 30-60 days, move your domains to another parking service and try them for 30-60 days. You'll find a happy home for each domain eventually!