Infoplease.com, a free, authoritative, and respected reference for Internet users, provides a comprehensive encyclopedia, almanac, atlas, dictionary, and thesaurus. Infoplease.com contains facts on all subjects including sports, entertainme...
A useful resource: I don't know exactly how or where about.com gets all of its content. But I do know that it has simple, useful articles on almost every subject I search for. I've used it help make travel plans, research snowboards, and compare universities.
My biggest complaint is the site's layout -- way too many ads and articles are often spread over multiple pages to increase the ads count. It's annoying but still a useful resource.
Annoying but useful: It annoys me when about.com articles are in the top of my google search and so it annoys me even more to admit that most of the time the articles are useful. I think the reason I dislike using it has to do with the layout of the site. But I always feel tricked into learning.