IMHO, the best way is through your network. Great people know other great people, they tend to stick together. So find some great people and get the word out. I'd also suggest having a couple bullet summary of your personal value prop handy.
If you'd like to be more in the startup space then look at startup blogs for networking events in your area and attend. If you're in Seattle, you can attend things like OpenCoffee at Louisa's. I went a while back and met a few folks that were getting plugged in to various projects that eachother had going. I had coffee with Andy S (TechStars) that day. Your portfolio (which may or may not include open source contributions) will help seal the deal, but unless it's really prominent is unlikely to find the leads for you by itself.
If you're looking for enterprise level contracts, then probably the best thing you could do is go through a contracting agency to start. Most big companies don't hire independent 1099ers anyway, many times for insurance reasons (of all things...). Again the point always goes back to building your network so the first gig or two might not be what you want but keep in touch with the people you can. Make sure your gigs are at the best possible companies you can find. Again back to Seattle, Microsoft is awesome to meet great people at and they contract relatively heavily. Also the bio tech's are no doubt in need right now.
Good luck!