I peaked at about the weight you are at now, and I went through a couple big-store bikes before I picked up a used decent bike, so its good to see you hunting craigslist for a decent bike. IMHO just about any bike that fits you reasonably well will be fine. For me, when I was that size the suspension forks out there didnt have lockouts and certainly were not strong enough to hold me up, so I ended up taking out all the elastomers and putting in wooden blocks that I had a friend shape to size with a lathe. Not sure if they still use the elastomer and washer approach anymore, but if they do this might be something to consider.

If you end up really getting into biking, you should be able to turn around whatever bike you buy for around the same price, then apply and new savings on top of that and trade up a bit. I did that a lot while Iw as still in school. A few cleaners, some lube and a bit of elbow grease could end up netting a nice profit on most of the bikes I bought.

Good luck.