I've got a little RCA VR5320R that runs on AAA batteries. A set of batteries lasts in excess of 12 hours. I can leave that running from the moment I leave the house, until I get home. Up to 200 hours record time, built in USB to download to a hard drive. Its about $30 on Amazon, including shipping.
Just got Steel Magnolia a new one from one of the office supply stores, really snazzy; don't have make & model available, because she has it with her. But, it does leave me with an Olympus VN7000, which doesn't have USB interface, but otherwise is a nice little unit- 2GB memory (80+ hours HQ), 39 hours on a set of AAA batteries. It needs a home (hint, hint).