Years ago I spent quite a bit of time with lower-end document scanners and document management systems. Back then there was nothing good for less than $1000, and very little between $1000 and $10,000. HP's solutions were quite horrid, they doubled as paper shredders.
So I was quite interested when I used a Fujitsu fi 4010CU. This USB 2.0 scanner is quite compact and quiet, and it's done well for low volume document scanning at our office. The bundled software is clumsy, but with some tweaking I could get quite nice B&W PDF results (I know what I'm doing though) using Adobe Distiller. The software is not as sweet as the discontinued Scan input software Kodak bundled for years, but it worked.
And the 4010CU is less than $600.
That led me via Google to this site, where one can run a query that reveals many alternatives: Scanners - searchable guide to high-speed document scanners
Nice site! Too bad OS X support is so lacking ...