While doing some research today, I came across Mark Liberman's class notes for his Introduction to Linguistics class at Penn.
Liberman is the main proprietor behind Language Log, a must-read for anyone interested in language and a place where copy editors often are skewered for their rigid pedantry (and as I are a copy editor as well as a professer, rightly so I'd sometimes say).
But the point here is to take a look at Liberman's "Language Wars" class notes. Make these must reading if you really care about language and about understanding the many complex issues in tracking -- and adopting -- changes. They are simply excellent in summing up what too often is labeled as "prescriptivist vs. descriptivist" for shorthand.
While you're at it, mosey over to the alt.usage.English newsgroup home page for much more than a string of posts. The best have been collected into well-reasoned FAQs on the separate Web site. Mini-FAQs provide quick-hit information, while the larger FAQ compiled from Mark Israel's work provides longer explanations, and an excellent supplement has later entries.