Isn't it unrealistic to hope to crack SHA256?
No.
It all comes down to what's hashed. If it's a whole document, well good luck. If it's a word or two it shouldn't be too difficult if it's just a single hash.
When someone encrypts something its different to a hash though
OP mentions truecrypt. If something is encrypted with AES+twofish+serpent or whatever it is(the default setup for truecrypt), isn't that into the millions of years to crack?