- Answers.com (People) -- Free Site - Does not have popups but does have banners. Entries are separated into two groups: people, and all other subjects.
- allRefer Reference, part of allRefer -- Site has many pop-ups and banners.
- Encyclopedia.com, part of eLibrary -- Site has some banners, but no pop-ups
- Information Please, part of the Family Education Network—Site has banners
- The Free Dictionary -- Site does not have any advertisements, but some content only available with a subscription
- Yahoo! -- Site has a few banners.
- Preface to the 6th edition -- gives more information on the current edition of the Columbia Encyclopedia