Hi, Namejet have exclusive agreements with Enom and Network Solutions for any domains that are expiring to be offered at their site for auction, funny enough GoDaddy are barely capable of catching their own expiring domains in my experience. Snapnames used to have this arrangement but seem to be reduced to just doing private auctions after been taken over, Pool are also another dropcatcher. I used to participate alot in the old snapnames auctions and got some good domains but am not a big fan of Namejet, you're gonna need deep pockets and will also need to be verified to bid above $1000.
Namejet with Enom also have the up and coming ".tv" corner to themselves with some premium .tv domains being offered from $500 to $15,000 or more per year