Phil,
This here is a pretty cool bike by Giant. Its the Cypress LX I believe, and is in the high end of your price range. 700c wheels are a good size for commuting, it gives you the benefits of a fast rolling 700c roadbike, but you also get basic front suspension and disc brakes, so you can run a much wider tire than a roadbike which is severely limited by brake clearance. Components are pretty decent overall, and you're in a more comfortable position than a conventional drop bar roadbike.
Avoid Schwinn like the plague... they sold out to a Asian conglomerate that makes mostly "Huffy" quality bikes these days. Specialized, Trek, Giant, Kona, Jamis, Gary Fisher, are all good and fairly common brands in the bike industry these days.