The simplest method is FTP. Mac OS X has an FTP server built-in (turn it on in the Sharing Preference Pane,) and just get an FTP client for the 68k.
(I also have an ultra-simplistic web page set up to host files internally that even Mosaic 1.0 can connect to.)
(I also have an ultra-simplistic web page set up to host files internally that even Mosaic 1.0 can connect to.)