Steve, I've been using this for my projects:
* Piotr Fusik (http://atariarea.krap.pl/x-asm/inflate.html, inflate
6502 code).
* Rich Geldreich (http://code.google.com/p/miniz/, deflate C code).
Fusik's inflate code is just under 512 bytes. ~768 bytes are needed
as a scratch area and 10 page zero bytes for internal vars. The code
decompresses only.
Geldreich's C code is what I use to compress the data on my Mac. I
get the same level of compression as gzip/zip.
Fusik's code is written in his own ATARI assembler. I ported it to
CA65 if you are interested. It is easy to use as is checking for
errors.