Basically Steve is right - you have no revenue because you have no traffic. This is quite a common problem on the web. You need to get more links into your site.
With other sites I've run, one of the best ways to get more traffic is link exchange. I was running a Thailand related site and one of the best sources of traffic I had was a link from a Thailand based online newspaper.
Once you have traffic boosted I also think it's really important to get your page view level boosted. Although this is proportional to traffic, maximising page views can boost your income considerably.
Several useful techniques for boosting traffic have already been mentioned in this thread, so implement all of them.
You might also find the following article of interest:
The Truth About AdSense