Right now everyone is talking about facebook, social software, and what have you. But most of these sites aren't making any money, and they never will. It's basically a really crowded market with no clear income model unless you're really big.
Find a niche that hasn't been exploited and create software that solves a problem in that niche. B2B is probably the best place to look - if you can come up with a piece of siftware that can either save a company money or make them money they will be happy to pay.
If you have ever seen SAP's implementations of ERP systems you will know that the B2B software out there is totally crap, and that it should be possible to come up with something better. And there are real companies willing to pay real money for your software.
There are plenty of people and companies and people that want and will pay for useful software, you just don't read about them on digg or reddit because they aren't sexy and cool.