They're not generic hashing chips, so any sort of 'quickly hashing every file' is not applicable. They couldn't even do a single SHA256 hashing of a few bytes, as the hash isn't actually returned.
The output of a SHA256 hashing is supposed to be sufficiently unpredictable that any task you think you could accelerate by exploiting what the ASICs do and working back from there is also not going to fly.
This question has pretty much been asked since before ASICs popped up, and a Google search for 'bitcoin asic other uses'* will readily pop up some suggestions, most of which are invalidated or just unlikely to be practical.
As an example, as one blog post postulates:
* the hashes are generated with sha256(sha256(x))
* salt + password = 80 bytes
* the hash starts with 4 zero-bytes
I think some generic discussion posts around here come brrrr-weather time may have the only reasonable answer (beside "no") so far: they're pretty good as heaters.
* That search also returns this same question, over at StackExchange, which elaborates on the question a bit: