Craigslist.
I feel your pain on the budget question. I am riding what some affectionately refer to as a "bike-shaped object" or a "department store beast" (i.e., a Target Schwinn), due to budget constraints at the time. Looking back, I wish I'd done more research and looked for a deal on Craigslist. Since I bought the bike a year ago, I've had to replace the wheelset and do lots of tweaking to get things right. The same money I spent on my Target bike could have gotten me a much better, if used, bike off CL that wouldn't have given me nearly as many issues, I'm sure.
Here's some Treks in my area just as an example (not sure where you are):
http://washingtondc.craigslist.org/s...min&maxAsk=250