Craigslist a it a bit of a lottery and to win you have to buy a ticket everyday. Of course just looking is free except your time.
If you want a Walmart bike sometimes you can get them for cheap rarely ridden on CL for a fraction of the price. I bought one of those Target Schwinn Varsities they sold a couple years ago a few months ago for $50. It still had the pricetag on it clearance for $130. I rode it for a few days around and it was ok I just didn't like it most how it rode. I adjusted the brakes so they stopped significantly better than before and and sold it for like $85 which I though was a pretty good price. It didn't last long. It looked nice of course, was basically brand new and all the consumables were basically new. If that was the only bike I had I really couldn't have complained about it.
I had a Huffy Mountain bike a few years ago I rode alot as a commuter. I had to fix a couple things on it, but I don't remember it ever letting me down. Of course when I acquired a Used Gary Fisher mountain bike a few months later that was the sweetest thing I I had ever had and it was probably their lowest model or something. I can't remember what it was since I only had it for a few months before it got stolen. I think I spent like $10 or $15 at a thrift store on the Huffy and I got my money out of it. I gave it to a friend that never owned a bike and she was overjoyed.
I was dissappointed to see Walmart didn't have that $200 Schwinn hybrid that was basically outfitted to be a commuter with fenders and rack. for that price it wasn't bad at with the accessories. I was tempted to buy one of those Mongoose Cachet Signlespeeds and now that they are only $129, but I have no need for one.