Do a search on the forums here as I know there have been a decent number of threads on this topic in the past.
In my experience Connectix
Doubletalk (mac product) works great in Classic. If your macs are running OS X then you can natively connect to Windows fileshares by choosing the "Connect to Server..." option. Install the
Samba Sharing Package to let your PCs natively connect to mac OS X fileshares. Samba is free and opensource and the people working on the SSP have made a great and easy control panel to configure and manage Samba that is also freeware.
Other products you might want to consider are
Dave (mac product like Doubletalk for Classic and OS X but harder to configure

). On the PC side the main product you can install is called
PC MacLan which will make the PC appear just like a mac on an Appletalk network. I believe you can share printers with that one too.
Finally, I still like using
Timbuktu Pro. It's a very full featured remote control application (think VNC but corporate with a lot more features) for macs and PCs and allows you to exchange files, messages, remote control, intercom, etc. It's great for managing servers that are running a different OS than your desktop (ie no Terminal Services or Remote Desktop).
Good luck! I've used all of these products except for VNC (I'm planning on that one though

) and can possibly answer some of your questions.
Gaidin