One of my favorite sites on the Internet is About.com. They seem to have columnists on most any topic and the quality of the writing is universally good. I should mention that I sometimes write for their Adult Education site*. Kimeiko Hotta Dover, the Adult Ed guide has done a tremendous job of creating a useful site.
Another amazing site at About.com is the Distance Learning one hosted by Jamie Littlefield. If you go now, you can see the 4 Types of Online High Schools.
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*Quite by accident, I discovered that an article from some time ago, is now the featured article. See: How to Get a Degree Fast.