Britannica Online Academic Edition combines the complete Encyclopedia Britannica and full-text articles from various periodicals with select Web sites plus a host of reference tools including the Merriam-Webster's Collegiate Dictionary and Thesaurus.

Columbia Encyclopedia(6th ed. 2001-2007) contains nearly 51,000 entries and more than 80,000 hypertext cross-references. It is available through Bartleby.com.  

Funk & Wagnalls New World Encyclopedia offers over 25,000 encyclopedic entries covering a variety of subject areas. It is updated annually.