Domain parking pages
I have tried putting DomainSponsor parking pages on a few domains registered through my Tucows reseller account. The whole bit has been running for a few weeks with hardly any success.
Out of the people that access the pages, no one seems to be intererested in actually using the directory links displayed, hence there’s no money in it for. I guess this only really makes sense when you can drive a larger volume of traffic & domains, and/or have more keyword-specific domains than I do. But I guess it was worth a try 
I’d have to say that I have had more success during the 100 and something days we’ve had Google Adsense on two of our sites. Basically I put the ads up there when I realized that both sites are rather popular search results for specific terms, but in the end I don’t provide what the people expect to find. So when they end up on those sites, they leave right on the homepage.
With Google Adsense, I can give them some links that are most likely related to their search, so in the end they might find something they are looking plus maybe earn a bit off money by doing so – quite a fair deal for everyone involved, including the advertisers.