I think most professors are okay with students citing blogs in class papers (as long as the blog post is written from a credible source).
However, I’ve had a couple professors that didn’t allow anyone to cite blogs or Wikipedia articles in papers. They felt that those websites could be easily changed, and weren’t worth citing.
That’s why you should always check with your Prof before using a blog entry in your works cited list.
Once you have approval to reference a blog for your essay, here are some ways to cite blogs according to MLA and APA style guide:
Lastname, Firstname, “Title of individual blog entry.” Weblog entry. Title of Weblog. Date posted. Date accessed (URL).
Lastname, FirstInitial. Title of individual blog entry. Retrieved January 1, 2007, from http://www.blog.com
For more examples of how to cite blogs, check out the Purdue teaching resource page.