I just did a little searching around, and found a handful of OSRAM panels which looks neat.
One series is 128x64px at 36x18mm viewable, with external dimensions on the panel at 49x31x4mm, which seems decent for gumstix-type apps, though it's maybe a touch bigger than one might like for something like a waysmall cased computer.
The other is 128x64px at 61x30mm viewable, with external 90x47x4mm -- bigger than the above, but probably more useful in some kinds of situations. Looks like digikey carries them (search for model number prefix OS128064PK) for not too expensive a price.
We'll definitely be looking at using these things to build into cases I think, as we start rolling cases out...