One step above the most basic manual-feed scanner design, the Brother DSmobile 720D ($149.99 list) adds the ability to duplex (scan both sides of a page at once). That gives it more capability than, say, the Visioneer RoadWarrior 3 , which lacks duplexing, but less than the Editors' Choice Canon...
Low cost; Portable; Duplex (two-sided) scanning; Comes with capable document management software
Although it comes with business card software; it doesn't handle business cards well