Freelance bidding sites are one of the ways that freelance writers get started. There are also lots of writers who work almost exclusively through them and do quite well. I've used two of them consistently for both work through the site and to secure regular clients. Now that I think about it, I'd say about 90 percent of my regulars have come to me through an initial bidding site project. Of course, some sites are better than others, and no site is identical to any other. Here's a basic breakdown:
RentACoder- This one is free to use and was the first bidding site I tried. The well-paying gigs aren't as plentiful as they used to be, but they can still be found if you're persistent. What I usually do is check the buyer to see if they've been outsourcing to India/Pakistan/Bangladesh for content. If they have, I pass. If not, there's a chance that they may pay a decent wage. This site gets knocked a lot because it has some of the lowest-paying work you'll ever see. And, yes, it does. But, there are definitely gems to be found amid the muck. I've gotten some of my highest-paying gigs through RAC.
Elance- This site was great for a long time, offering an enormous amount of jobs, though they did require a monthly fee. But, the fee could be knocked out quickly as the jobs came in. They still do have an enormous job pool of diverse writing gigs. Some of them are extremely well paying. I've done pretty well here and gotten a lot of regular clients. Unfortunately, they recently tripled their fees and reorganized into a complicated mess that results in less opportunities for gigs unless you pay a lot more. There's still potential there for someone with a lot of experience. But, for new writers who won't be getting as many jobs at first, the cost will likely far outweigh the benefit. Right now some of the new fees are being waived until March. If you've never used the site and want to try it, I would advise signing up right away to get a few feedbacks under your belt before the hideous rate changes smack you down.
Guru- I've heard extremely good things about this one, though I've never used it. The only reason for that is that I have a problem paying for more than one bidding site at a time. I'd have to start buying generic chocolate, and no one wants that. Trust me. I have heard it recommended so highly so many times that I'll likely be jumping on board as soon as I jump off the Elance train wreck in March. The fees are comparable to what Elance's used to be back in the day.
GetAfreelancer- I've heard mixed things about this one. The fees are quite low, and paying just $12 a month means you don't have to pay any commission. The problem is that I've never seen a gig worth the money on this site. It may be like the RAC weeding out process, but wherever the well-paying jobs are, I'm not seeing them. I've also heard from several people that getting stiffed isn't uncommon there. It might be worth a try, but overall I'll have to pass.
Two others to try:
Just stay away from these guys: http://www.gofreelance.com/
They are not a bidding site but try to look like one. Their reputation under a different name was horrendous online due to scam concerns, and they have changed their name since that time. I can't prove that the bad reputation and the name change were connected, but you do the math.