Sparkfun does PIC microcontrollers. The SHA256 algorithm isn't all that complex, so it might well fit on one of those. It won't be fast, but probably more than a few kHash/sec.
Alternatively, looking beyond Sparkfun, the TQFP FPGA's are just about within a hobbyist's scope, tricky to solder but not impossible, So you could get up to a few MHash/sec. Just don't think of using the BGA packages. Nightmare, though it has been done, I recall seeing a post on this very forum, he used a skillet to solder Spartan6 LX150's
Anyway, joking aside, if you're going for that, why not homebrew something with one of Biftury's new chips (yes, I am considering it, but seeing as I've only got 0.,5
BTC to play with, I'll have to wait for a single chip group buy
)