Since I can't find a small enough Smalltalk, I decided to implement FORTH on my TI92+ and hope for a Smalltalk implemented in that :) I'm certain someone's done it.
Forth can be built from a set of primitives - probably what about a dozen. Then you just build your vocabulary from there. Lisp also can be built from a small number of primitives, but getting to a useful state of affairs requires a much larger library.
Don't know if it's useful, but there was a link posted on [link|http://lambda.weblogs.com/discuss/msgReader$8536?mode=topic&y=2003&m=9&d=1|bare metal Smalltalk]. Presentation was a bit flashy for my tastes, so I never got past the first few pages.