right now i work with 2 startups and 1 large company, as well as do occasional consulting with another large company (this is usually less than 5 hours every month). i'm all about simplicity and breaking things down into small pieces, so on all projects i am able to deliver and launch features regularly with 10-20 hrs of work a week on each. my total billable hours for the week usually are in the 40ish range.
i've found all the work through referrals pretty much, so i can't say exactly how to find it for others. i will say put as much as you can out in open source, that is the best "sales" technique i've had (often "referrals" have come from someone i've only interacted with in the open source community). also, be consistent with your deliveries, and open and honest about scheduling, as well as when something is going to take longer than you estimated. surprisingly few contractors are good at communication it seems. often i come into projects for people who were abandoned by a developer and even when they were working together only got spotty communication from that dev.