Tools described on this page are recommended having been used actively on the platforms shown.  They are either free and / or open source.

7Fzip file compression

Application Link Windows version OSX (Power PC) version
7Fzip file compression logo
 http://www.7-zip.org 9.15 beta none

Filezilla

Application Link Windows version OSX (Power PC) version
Filezilla http://filezilla-project.org 3.3.4.1 yes OS X 10.5 and above