The Abacist's Guide to the Internet(All links have been verified in July 2004)
A site with lots of information and stories around the abacus and it's use, including history, frequently asked questions, articels, and analyses. Lots of links.
A discussion group on the Yahoo site dedicated to all aspects of abaci and especially sorobans (the Japanese Abacus). You need to register in order to read and post messages.
A site dealing with "Traditional Mathematics in Eastern Asia". It has a wealth of texts on Japanese mathematics, mostly historical texts. Nearly all material is in Japanese.
A german master of calculation who lived 1581-1655. The site has some descriptions of reckoning on lines.
A facsimile of the famous book of Adam Riese teaching arithmetics using a tablet similar to an abacus.