iChat

Yeah, but just think about how it'd improve iChat AV. ...

'I forgot to ask if this could be done over the internet?' - if you want to leave open a connection between the two Macs then consider 'Chicken of the VNC (client)' and 'OSXvnc' (server). Another way is to turn ON 'System Preferences' 'Sharing's 'Services' tab's 'FTP Access' feature. If you are only interested in (streaming) sending files between two Macs - then consider...