I was just reading Shawn's blog and he mentioned an idea I had never thought of but it's a good one. Monetize those 404 error pages by adding affiliate links. Also some good tips for monetizing domains.
Affiliate Program Tip Blog - Affiliates Making Money Off Parked Domains
"I've frequently encouraged affiliates to make use of their 404 error pages by serving up some relevant affiliate links to capitalize on the traffic that accidentally hits those pages."
http://www.affiliatetip.com/blog/archives/affiliates_making_money_off_parked_domains.html
Affiliate Program Tip Blog - Affiliates Making Money Off Parked Domains
"I've frequently encouraged affiliates to make use of their 404 error pages by serving up some relevant affiliate links to capitalize on the traffic that accidentally hits those pages."
http://www.affiliatetip.com/blog/archives/affiliates_making_money_off_parked_domains.html