Word of mouth is the most powerful way to get business, of course. So the first step is to let the people you know know that you're available. Tell the people who might need your skills that you have them; if they don't need you, they might know someone who does. (This is a good use for LinkedIn.)
Have an elevator pitch ready that summarizes your tech specialties (e.g. HTML5, Dojo), business expertise ("have created several websites for realtors"), and a sense of the best match that hints at your rate ("affordable for small businesses"). Have a web portfolio ready. Update your LinkedIn page.
Depending on how much "a bit of extra cash" you can get started with sites like elance.com but my sense is that the money isn't all that great. (That perception might be inaccurate.) If all you're looking for is "a little extra" and an opportunity to expand your skills, it might still be a good idea.