The following text is from deank, the developer of multiMAN. He claims in multiMAN version 04.15.00 it is possible to connect 2 PS3′s (anywhere in the world) and copy or share data without a USB drive or PC.
Here is something some of you may find useful
Some of you used “Network Servers” option in “Settings” to connect to a PC running ps3netsrv to copy files, play ROMs, play music or view pictures.
Now it is possible to connect to ANOTHER PS3 (running mM 04.15.00) be it in your local LAN or anywhere in the world.
You can copy/share data with another PS3 if the ‘server’ PS3 is running mM 04.15.00 and the ‘client’ PS3 can be using mM 04.00.00 or later.
You can backup games directly from the BD Disc of the server PS3, view photos, play music, install PKG files, copy games, access all devices connected to the server PS3, if you’re on cobra cfw you can even play PS1/PS3 games or Blu-ray/DVD movies stored on the server PS3.
You can transfer game backups, movies and data from one PS3 to another without a USB drive or PC.
All in all – you can transfer/share data between to PS3s on CFW via the /net_host feature of multiMAN.