Theres some great tests listed here:
Draft Special Publication 800-90B - National Institute of Standards
http://csrc.nist.gov/publications/drafts/800-90/draft-sp800-90b.pdf
In particular the min-entropy, partial collections, markov (useful for non iid sources), collisions, and compression tests.
The issue with the markov test is the constraint on bit size of the sample. Too bad, it'd be handy..