It has been known that my one time audition coach, Mr. Simon Dunmore, actually posts to the forums here from time to time (he was most recently logged in to discuss his opinion on headshots), but he won't necessarily see this thread, so I will do a bit of promotion on his behalf. Simon produced a set of books (still widely available, I believe), which contain selected excerpts from Shakespeare (with commentary) that he deliberately chose because they are not overused. There is a female speech book and a male one. As he used to tell me, following a couple of decades' worth of holding auditions, he had grown to see the need to encourage actors to avoid doing the same tired old material, when they might make a fresher impression working on something less well known. So, one idea might be to get hold of a copy of his book.
His personal website, which is at http://www.btinternet.com/~simon.dunmore/, usefully lists Shakesperean monologues that he feels are overdone, and perhaps to be avoided on that basis (although, as he points out, it's not *always* the case that you should avoid doing a familiar speech simply because it's familiar, if you are convinced it suits your casting and you do it well!). Seeing all the monologues listed might get a bit disheartening, although it may spur you on to buy the book/search through a complete works in unusual places for speeches that strike you.
Simon also has a great list of playwrights whom he feels are good authors to use for audition. To some extent, with the Elizabethan/Jacobean authors, there are only so many that *can* be listed, but you will find all the names in an easy to reference manner presented here, and although there's no indication of what parts are available in which plays, it can certainly start you off on the right track to know which playwrights are available! Webster, Marlowe, Fletcher, Kyd, Massinger etc. might all be worth mining for underused material, and there are many others - you might even, at a pinch, utilise some Restoration era material - although you will have to check what parameters the drama school in question considers 'classic'. Some, it must be said, actually go so far as to say 19th century material is acceptable, or accept material as ancient as Greco-Roman drama.