I run a small village of microsites on different topics, it's sort of an experiment to see what sorts of traffic I can get. I had the domain jackvalenti.com, which I bought on a whim and set up an unofficial page about Jack Valenti there along with AdSense ads. Well, after spending nearly $100 on the site I am averaging ZERO visitors per day, so to avoid some site fees I am moving the content to a subdomain instead. From now on Jack Valenti page will be here instead.
Another more successful, but still an infuriatingly unsuccessful small site I had was a sweepstakes site. It runs on pligg and used to be in English. Every day I would check the stats on Google Analytics and every day I was getting around 200 visits, but nearly 100% from Finland through one nice inbound link I managed to get, so I will yield under the pressure and turn the site into a Finnish site to serve those visitors better. From now on it will be here: kilpailut.
One thing I have learned while trying to promote my sites is that people respond well to prizes. I had a forum that I was spending some promotion efforts on, but hardly nobody registered to that forum. Then I offered a prize for registering and posting on the forum and suddenly people (in the target group, not just prize scavengers!) started registering and posting. Prizes are expensive though, difficult to say if it makes sense to give them out. On a forum it is very important to reach a critical mass of posts at first, so it may help at that and possibly pay off in the long run.