From Smith Micro:
StuffIt Expander supports a wide variety of files you download everyday on the web or receive in email. More than 30 formats are supported including archives created with the latest StuffIt 2011, WinZip, WinRAR, 7-Zip, 7zX, iShrink, SimplyRAR, Rarify, Rucksack, iArchiver, BetterZip, RarMachine, GUI Tar, CleanArchiver, Springy, TarPit, RAR, Ez7z, Keka, sArchiver, and many more, including the compression utilities built into recent versions of Windows and Mac OS X. Encrypted archives? Expander handles those too. Segmented or split archives are no problem for Expander. Just drag, drop, and you're done.