John,
Macs can UNzip files but there doesn't seem to a Mac version of the ZIPing
program. There is a PC (freeware) version of the Mac Extractor program
which will deal with both Stuffit and Compact Pro archives. As a result,
I'd favor standardizing on two formats depending on which one you can
produce on your machine. I'd prefer Compactor Pro as the Mac format (as I
have it) and believe I can deal with either ZIP or ARC files (although I've
only actually read ZIP ones so far).
I'd also suggest that copies of the freeware un-compressor programs be
available in the library in uncompressed format.
Mike