Letters to the Editor
Everyone's got an opinion, and a letter to the editor of the local paper is a most convenient way to express it.   Given the length restrictions, I consider a letter to the editor to be the expository equivalent of a haiku.  A good letter requires focus, clarity, conciseness, and precision; one must get in, make one's point, and get out.  As such, the letter to the editor is excellent practice for good writing in general.
Literary Commentary
When I returned to UNCG in 2005 to finish my B.S. in Finance, I was required to take a couple of literature classes.  I resigned myself to taking them; in high school, English was second only to P.E. as my least favorite subject.  Oddly enough, I found that I actually enjoyed them!  I enjoyed them so much that I continued as a second degree undergraduate to get a B.A. in English.  As a bonus, all of the discussion board posts, short responses, papers, essays, and other writings that are de rigueur in the formal study of literature make legitimate web content.