Have you tried surfing/searching for Samba - that seems to be one of the main sharing systems - don't use it myself, but if you do a search here at LQ, i'm sure you should be able to work out if it's what you're looking for.
Failing that, google for samba, it should at least come up with the home page for the project.
edit - just done a quick search here, and I found this link
in a post by PEACEDOG. I'd say that samba is probably the facility that you're looking for. - /edit