Sandpaper is a form of paper where an abrasive material has been fixed to its surface. Sandpaper is part of the "Coated abrasives" family of abrasive products.
http://en.wikipedia.org/wiki/Sandpaper

Uneeda offers a wide variety of superior quality coated industrial abrasives for every sanding, grinding and finishing application.
http://www.sandpaper.com/

This article details everything you ever wanted to know about sandpaper. It's written in a F.A.Q format and is easy to read.
http://www.woodzone.com/articles/sandpaper/index.htm

The Newsmagazine of Southern Ocean County - Long Beach Island. Click to view SandCastles Real Estate Guide! Click to View The SandPaper
http://thesandpaper.net/

Offers wet-dry sandpaper, hook and loop and stick-on discs, cloth-backed belts, drum sander rolls, and bulk tack cloths.
http://www.sandpaper.ca/