Undiscovered Classics?

Since the Internet is making scores from all eras, whether famous or unknown, so easily available, since it's possible to with a few clicks to look up lesser known works or research a composer who's name you've only heard in passing, there must be a wealth of "undiscovered" classics being uncovered.

Have you found "old" compositions on Musicalion.com or elsewhere on the net that have changed your feelings about composers you thought you knew? What about compositions or composers that aren't well known--but should be?