Do you have any abandoned projects? If so, what are you going to do with them?
I also have a bunch of domains for side projects - those I usually hold on to, just in case I have time. Granted, there's always sedo.com as a good placeholder.
(some used to be full sites, some were just because I liked the name, and some were for projects I planned but fell by the way side)
* bgnm.com
* bigjibs.com
* billero.com
* bkexp.com
* boardingnation.com
* bubblerr.com
* costli.com
* divbill.com
* doldr.com
* elsewher.com
* guzzed.com
* fuelrr.com
* fourbean.com
* infilter.com
* revveo.com
* roqem.com
* shiftbase.com
* tabalizer.com
* MeetTheDress.com
* tweetfrag/fragtweet.com
* hackmyjob.com
That last domain has put me through at least 3 or 4 ideas, and nothing has really jumped out at me. That's probably the only one I'd hate to lose, but at this point I'm not sure what I'd do with it.
Now, as far as what has been built:
TweetFrag/FragTweet
This started as a notification service so my friends and I could meet up in online games. I built a quick Ruby on Rails application using Twitter's oAuth to connect and send out game details. It wasn't anything mind boggling, but the concept worked.
MeetTheDress
This one was for my wife, since she's practically obsessed with clothing. She wanted a site where she and her friends could post photos of themselves all wearing the same outfit. The idea being that others could see how the outfit looked on different body types. What can I say, I'm not that enthusiastic about clothes? :)
HackMyJob
Bought this domain on a whim. I had started a job board that was integrated with HN. I still have the code somewhere, but being that I was just learning Rails its hacky and borderline unpublishable. The other idea for this, which a friend of mine suggested, was a site for job automation scripts and hacks.
There, substantial evidence of actual projects that actually suit the domains they were built for.