I'm starting my last semester of library school in August and will graduate in December. When should I start applying for jobs? Is it too soon to start now? Thanks!

I agree with BCG--start now if you qualify. You definitely should be looking seriously, and working up your resume (if not already done).

I suggest you write several versions of a cover letter, for various types of positions that interest you. I would also suggest that you write a mega-letter (one that covers every bit of library experience you have, and all other experience that translates well into library skills. You won't use it as a real letter, but it gives you the bases for all your personalized letters. You can get your cover letters reviewed, which will help you see them differently---and that is very helpful.

Thanks everyone!