The Examiner compiles the fifty greatest examples of authors insulting other authors.  A few of my favorites:

Noel Coward on Oscar Wilde: What a tiresome, affected sod.

Ernest Hemingway on William Faulkner: Have you ever heard of anyone who drank while he worked? You're thinking of Faulkner. He does sometimes -- and I can tell right in the middle of a page when he's had his first one.

Samuel Johnson on John Milton: 'Paradise Lost' is one of the books which the reader admires and lays down, and forgets to take up again. None ever wished it longer than it is.

And the very best, Mark Twain on Jane Austen: Every time I read 'Pride and Prejudice,' I want to dig her up and hit her over the skull with her own shin-bone.