If you have a bike co-op (volunteer community bike workshop) in the area, they are a great resource for getting good used bikes at a reasonable price or possibly in exchange for volunteer labor.
Many local bike shops take trade-ins that they resell at a decent price. This is a good way to go if you don't have much experience as they can help you pick the right style and size of bike for what you want to do. LBS used bikes are usually lubed, adjusted and checked for safety before they are sold, something that can't be said for Craigs List, pawn shop, or yard sale bikes. $200 or less will get you a good used bike from an LBS with enough left over in your budget for a helmet.
Craigs List is a crap shoot, but you can find some good deals. If you don't have much bike experience, see if you can find a friend who does to go with you.
I agree that staying away from department store bikes is good advice. I currently own a few used brand name bikes and have owned others in the past including old Treks, Specialized, Schwinn, Giant etc. I'd ride any of them before any bike from WallyWorld or other big box store.
Last edited by Myosmith; 02-07-14 at 04:20 PM.