Orwell wrote:
Yes, rsync, but you have to make sure you're writing to a filesystem that Linux and Mac will both play nicely with.
We have a Mac that syncs iTunes and iPhoto contents using rsync over ssh, which is completely problem-free. It uses a one-line script to incrementally backup to a NAS, shared by everyone.
We also sync a few work documents over Dropbox, for the sheer convenience - Dropbox works on an iPhone and (sort of) on other smartphones, but I would not rely on it.