Skip the Walmart and Target stuff. If you arent going to bang the bike much and keep it on pavement, I would get it used. Youll find something much nicer. If you want to get new, just check out the big names. All of their entry stuff is nonetheless the same except for the frame geometry. You must test ride it before you buy.

If you like mountain bikes, I highly suggest you get rid of the knobby tires and some smoother threads. And if this is solely a commuter, dont get one with a suspension. Suspension just costs money and that money used can be fore better components.