a couple people have mentioned a drops section of the forum, as one's trash can be another's treasure. do you see it as not worth the time investment to try to at least recoup a couple bucks on a $6 - $8 domain? You say you have thousands you are dropping. even at 1,000, let's say all .coms and you have a bulk registrar account, so that's i'd say ~6k bare minimum spent on this inventory. if you could sell even half of them at $2 a pop, that'd be 1,000 bones back in your pocket. The question is whether the time is justified for the money, or would be better spent on other endeavors.
I think for smaller-time domainers and the smaller your inventory in general that it seems more justified to try to recoup. For larger domainers with big portfolios it may not be as big a deal.
my first wave of renewals is creeping up on me (i started less than a year ago) I know i have some early registers that are not worth holding, but personally as i have a smaller portfolio and limited funds, i'll try to juice out at least a couple bucks from them if i can. Then again, if i have a domain that i feel is worth more than reg fee i'd rather see it get sharked at by drop-catchers than undersell it.