wheel - 2:54 pm on Apr 6, 2010 (gmt 0)
I think you need to decide if you want to monetize them, or just keep them from losing value.
If you want to monetize them, then I suspect you have to be an in-the-know parking service to make any money off them easily. Other than that, everything involves you actually spending some time on the domains. I don't think there's an easy route to monetization.
I've got a bunch of domains, and I know rarely let any expire. I put them on cheap hosting,throw up a wordpress site and have my daughter write a half dozen blog posts on the subject. Then I park them.