You can use the Finder File->Make Archive. This wil create a ZIP archive that preserves everything necessary (other ZIPpping tools do not!) as long as the program is unzipped on Panther and later. If your software is Panther and later only this is fine.
You can use StuffIt to create a SitX archive (note the X). This will preserve everything necessary (regular .sit without the X do not) and can be unstuffed with StuffIt 7 and later.
However the usual way to distribute software on OS X is on a disk image. Create a new empty disk image with Disk Utility, drag the program into the disk, unmount it, then use Disk Utility to make it a compressed disk image (you can also use hdiutil or DMG Tool for the last step to get higher compression). Disk images work on all OS X versions without third party software.