>>33
It depends. SBCL is probably one of the largest CL implementations when it comes to code size. ~8-10MB is more common for other natively compiled ones, but if you remove the compiler and other unneeded libraries, you get much smaller sizes. ECL (compiles to C->native + bytecode compiler/interpreter for when the C compiler isn't available) takes 500KB, but if you include other components the size may increase by some 1-4MB. ClozureCL is about 15MB. I'm not entirely sure about Lisp Works' runtime, but it's under 20MB. Allegro CL is ~13MB, but size differs depending on what you include and if you use a tree-shaker. Of course, if you were to use compression, it'd be much smaller. A more limited CL (Win32 only) called CormanLisp compresses its image with zlib, leading to a total 2MB size for the entire thing. Compressing a SBCL 32bit core makes the size go down from 25MB to 5MB.
If you only want a limited lisp interpreter, it could very well be tiny, see
http://code.google.com/p/lisp5000/source/browse/trunk/lisp500.c or many toy Scheme implementations (non-toy ones tend to be larger).