Have you looked into flipping them? If they are good domains, you can make a bit of cash from them. Or maybe pay-per-click search engines?
I have most of my domains redirected to my main website... because why not. Some of them aI'm going to use for future projects, others are from failed project that I dropped or got tired off, total, all my domains that are redirected to my website brings about 10~ hits a week or so, since I am a freelance web developer I would earn more from 10 "maybe targeted visitors" visiting my website than parking the website and wasting my traffic on ads that doesn't pay. Alternatively, you could redirect them all to an affiliate offer or something like that.
I've got a ton of domains just sitting around. Some of them I actually purchased way back in the day and have their own registered free Google Apps accounts still attached. Personally I actually don't do too much with them, but make a bit of money by selling google apps access to clients.