cmucl looked interesting - it claims to be very fast (compiles to native X86 code) , but does mention as an aside that it is slightly more memory hungry than some other list enviroments.
I fired it up, and the whole system crawled to a halt.
13227 hungerf3 64 0 1009M 154M RUN 0:11 54.73% 34.62% lisp
That damn thing allocated over a gig on startup, and was apparently trying to map the whole gig into memory. The in core memory was rising like crazy, and it was thrashing through swap like mad.
I never even let it get far enough to bring up a prompt!