Roman numeral converter
Electronic Reference Shelf
: includes the OED, thesaurus, almanac,dictrionaries.
MEL : Michigan Electronic Library
TheInternet Public Library (includes a Ready Reference Section)
Lots of material, confusing arrangement at REFDESK.COM
The Library Spot has a pretty good arrangement.
Library Resources -- Reference sources is just one useful link from this page.
StudyWeb has many links to resources.
Lib Docs ( of interest to librarians)