It has long been noted that style manuals and other usage advice frequently contain unintended examples of the usage they condemn. (This is sometimes referred to as Hartman's law or Muphry's law - an intentional misspelling of Murphy.) Starting from this observation, Joseph Williams' paper The Phenomenology of Error offers an examination of our selective attention to different types of grammatical and usage errors that goes beyond the descriptivism-prescriptivism debate. (alternate pdf link for "The Phenomenology of Error") [more inside]
Language Log lists all their previous articles about prescriptivism vs. descriptivism (or at least a lot of them), plus a link to Geoffrey Pullum's Ideology, Power, and Linguistic Theory [pdf].
The "King of English", H.W. Fowler wrote A Dictionary of Modern English Usage. Although "modern linguists are almost by definition incapable of understanding the function of a book like Fowler’s Dictionary", the "half-educated Englishman of literary proclivities" who just wants to know: "Can I say so-&-so?’" may now buy the classic first edition of the Dictionary again. An earlier book, The King's English, is free for anyone seeking advice on Americanisms, Saxon words, the spot plague, archaism or split infinitives.