If they are all parked and you aren't getting much traffic, your best bet is to sell them through the forums. If you feel that it's a great domain (e.g. worth > $1000), you could always create a premium auction on sedo.
You may need to promote a domain using the Featured Listings which costs money, maybe do it for your best domain and in the domain description add all your other domains.
So when a buyer looks at your Featured domain they can scroll and view all the other domains you have.