Absolutely agree. My spouse is an active contributor to an open source project. Often, someone will come into IRC asking for help, and soon realize that the scope of the problem is bigger than they thought. Their next idea: "I should hire someone to do this for me." If you have demonstrated your tech skills, ability to communicate, and willingness to help a client... you might get the gig.

It doesn't have to be open source. As long as it's a community of techies working together to solve a problem, being the Helpful Cheerful Person in the Neighborhood can lead to consulting work.