I have been a full-time paid RA for about 1.5 years and I plan to head to grad school next year. Just form my experience, these jobs typically go to somebody who knows somebody. If that doesn't happen, and they have to go outside of that circle, they then consider the people who have taken the initiative to either email a scientist at a lab, inquiring about if they need help. Most of the time, the scientist will be happy to have the extra help, however most of the time, you will have to start off as a volunteer. Many times, after 'proving yourself' the scientists are able to scrounge around and at least find you some money to pay you part time, however securing a full-time position, especially in this economy, is definitely a hard task. I did this, and I feel very lucky, and I think the job market has gotten more competitive within the time I started at my current job.
Best of luck, hope this helps. Long story short: start emailing people whose research you find interesting, and see if you can start as a volunteer, get your foot in the door, and see where you can go from there. Volunteering is probably better than working an irrelevant job, just for the paycheck (unless you need the $$$).