One tried and true method is just to schelp your skills to some employer. Open source hacking is usually evidence enough to get you a good job. Sometimes, the project is even strategically important to the company -- Linux and Transmeta, for example.

There are a lot of very sane reasons to participate in FOSS, even if you only cared about money. It helps in getting hired. It's terrific technical practice. It builds a large set of technical links not tied to any particular employer, whom you can count on for good advice. It keeps you at the cutting edge of good practices and new technologies. And if you're starting a startup, you can find great developers through it. You can gain major hacker and media cred by open sourcing things.

In fact, open source may be one of the only methods, besides hacking with people in college or at work, for finding good cofounders. This is only a hunch, but it's one I'm betting on.

The only thing is that you can't immediately make money by that one particular method, but usually it takes a lot of experimentation to find a good business model anyway, and the network effects and the trouble of hosting things is often enough to keep competitors at bay.