Macutil

macutil (often called macutils) is open source software for converting and decompressing some old Macintosh-oriented archive formats. It includes the macunpack utility, and others.

Supported formats
Supported formats include PackIt, StuffIt, Compactor/Compact Pro, DiskDoubler, BinHex, Zoom, Diamond, ShrinkToFit, MacLHa, Compress It, UMCP.

Editors' notes
macutil is old, and essentially unmaintained. Use with caution, especially with the more obscure formats. One issue with some (all?) versions of it is that its CRC validation routine is incompatible with most 64-bit C compilers:

$ wget http://cd.textfiles.com/garbo/MAC/ARCERS/CPTEXPND.SEA $ macunpack -v CPTEXPND.SEA This is "MacBinary" input. This is a "Compactor" self extracting archive. Header CRC mismatch: got 0x9e5d4be6, need 0x13d15eac