Hmmm... Which Craigslist are you using? Budget?

There are quite a few vintage Schwinn Varsity (or similar) bikes that show up around here. They'd likely fit your goals, although they might require a full tune-up.

Also used Hybrids.

Personally I like my "road bikes" for commuter bikes, but my quick jaunt to the store is usually 20 miles RT or so, and often more.