netatalk is open source software that lets computers running some sort of unix OS speak appletalk (Mac OS file/printer shareing). It is similar to Services for Macintosh under WinNT.

If you aren't using netatalk or SFM you should still be able to connect to PC shares from OSX by selecting 'Connect to server' from the Go menu and typing smb://IP_Address/sharepoint into the address area.

There isn't a SMB/CIFS browser (AKA Network Neighberhood) for OS X yet so you need to actually type in the address and share point like above. You also need the latest version of OSX (10.1) for this to work.

-Mike