Scanners are the simplest and most ubiquitous digital imaging tool. Scanners are used to capture ordinary prints and slides for use online. High quality flatbed scanners now cost under $250, and many can be had for less than $150. Typical scanners now offer 600-1200 dpi resolution, easy connectivity via your computer's USB interface, and reasonably good bundled software for imagine editing, OCR, etc. In addition, more specialized (and expensive) scanners exist for scanning long documents, and for doing high-quality scans of slides.

Flatbed scanners

Flatbed scanners are the everyday workhorse scanners most folks rely on. They can scan photos, documents, and some even havetransparency adapters that will allow them to scan slides.(But most flatbed scanners lack the resolution to produce truly great slide scans).

For current reviews of scanners, see:

C|Net - http://www.cnet.com/Scanners/4502-3137_7-0.html
C|Net's reviews are somewhat consumer-oriented, but pretty solid overall.

We've had good luck with the Epson Perfection series. Visioneer, Canon and HP are among the other leading scanner manufacturers. There are a lot of good choices in the $100-200 range.

Slide scanners

If scanning slides is important to your organization's publishing work, we recommend purchasing a dedicated slide scanner. While slide scanners can be somewhat expensive, they are capable of producing the truly outstanding image quality that is essential to creating persuasive high-impact materials.

There are several appealing choices at two price tiers: around $500 and $1000.. Advantages of the more expensive scanners include: slightly higher resolution and ability to deal with "difficult" exposures (i.e. lots of shadow, etc.), built-in "scratch/dust removal" technology, and more robust software. Recommended "low-end" slide scanners include the Minolta Dimage Scan Dual II ($500) and the HP PhotoSmart S20xi ($400). Recommended midrange slide scanners include the Minolta Dimage Scan Elite** (US$1000) and the Nikon CoolScan III LS-30 (US$770).

http://www.flatbed-scanner-review.org/
35mm_slide_film_scanners/35mm_film_slide_scanners.html
has some real-world (if somewhat wordy) reviews.

Also see http://www.photo.net/digital/scanners/for some more opinions from photo geeks.

Document scanners

Someorganizations (typically folks working with legal documents) frequently need to scan in long paper documents. This can be very slow with typical flatbed scanners. There are specialized document scanners that do this job quickly and efficiently. They're not cheap, but if you have to scan long documents frequently, they're well worthwhile.

The best resource we've found on this somewhat esoteric market is CD Dimensions' Document Scanner Comparison chart:
http://www.cddimensions.com/document_scanner/scanners.asp

Scanner Galaxy (http://www.scannergalaxy.com/) is an online vendor with a wide range of document scanners.