Encyclopedia - Britannica.com (the complete Encyclopædia Britannica online and more)

Almanac - Information Please Almanac

Maps - The Perry-Castañeda Library Map Collection at The University of Texas at Austin

Dictionary - WWWebster Dictionary

Medical Dictionary - Online Medical Dictionary from the CancerWEB Project

Thesaurus - Thesaurus.com (an online version of Roget's Thesaurus of English Words and Phrases)

Quotations - Bartlett's Familiar Quotations

Reference, Literature, and Verse - 
Bartleby.com: Great Books Online

Auto Repair - Chilton Library
(Click the "Proceed" button under INFOTRAC)

Genealogy - Ancestry.com
(Available only from the main campus or another member of Northern Waters Library Group)

Many More References -
The AIHEC Virtual Library: Reference Sites