Note: These installers are not compatible with MacOS 10.5 (Leopard) or any later versions.
For a copy of psync compatible with MacOS 10.5+, install DejaVu (I am not related).

Even better, learn to use rsync. Version 3 is finally usable on Mac and in some cases, like copying to another Mac, may be better than Finder (because of AFP limitations and Finder design, files copied to a remote volume in Finder have their create/mod dates changed, so you cannot use that for incremental backups).

This is how I use rsync, to backup a folder to my wife's iMac:

rsync306 -vaAXNhPi --del --rsync-path="sudo /usr/local/bin/rsync306"' local-folder eli-imac.local:/Users/Shared/macpro-backup

For this to work you have to have rsync 3.0.6 installed in your PATH, another copy installed on remote machine in /usr/local/bin and have your name in sudoers.

If you still want my old build of psync, click here