I posted on Craigslist this morning:
I’m a freelance tester. I specialize in test automation with open source tools:
Selenium, Watir, JUnit, TestNG, PHP, Ruby, Webrat, RSpec, Cukes, Hudson, Cruise Control, Ant, Maven
I believe in getting the job done. I can do all of the following:
* set up a web test environment (Linux, Apache, MySQL, Tomcat, JBoss, Passenger)
* install tools (Jira, Bugzilla, Confluence, xWiki, etc.)
* create test plans
* manage remote testers
* develop an automation framework
* implement continuous integrationCall me at 425-242-4304 or visit my website: http://one-shore.com/
-Aaron Evans
I haven’t had much luck with Craigslist in the past. Most listings under computer services offered are for either web design or PC services.
I’m curious what other freelancers do to market themselves, since this seems to be the biggest challenge to me.
Fijiaaron 
I think a lot of it has to do with your service area (geographically). If you are looking to be the go-to person in your town/city then joining the local Chamber of Commerce might yield results. Also, going to various user groups is also necessary. With freelancing, you are always marketing yourself.
On the larger scale, then building up your reputation in the ‘tool’ communities that you want to / are specialized in is important. Also being engaged in the testing community at large helps.
Speaking at conferences, writing for trade rags, producing a book are all other classic ways of increasing your profile.
Of course, from me, this is kinda theory as I’m only starting out on the freelance road, but it seems like sound theory.
-adam