If somebody was looking to develop their own file sharing application, but wanted it to use some service that already exists, which services are available to use freely? What does kazaa/winmx/bearshear use? What did Napster use? Is what Napster used still out there, available to use?

Any information is appriciated.

The Kazaa protocol is closed.
Attempts to duplicate it (i.e. to try developing a Linux client) were discouraged by the Kazaa developers.
Don't know about the other things you mentioned.

You can try using the eDonkey network.
It's not exactly an open protocol, but an open-source client (eMule) exists for it. You can learn from it and add to it as well.
www.emule-project.net

I've heard of something called open nap. Apparantly it's an open source napster protocol, that's still in use. Anyone heard of it?

No one uses opennap. I suggest you use Gnutella.

dcplusplus.sourceforge.net <-- open source file sharing client for Direct Connect network

along with many of the VB projects im doing, im writing a file sharing program.

basicly.... everyone is there own server... people tell others there IP or have there ip redirected and tell them that.

THEN a user connects to it and searches ther efiles.... for whatever they want.... then they can have a list of other users and it search there files for the same file to maximize upload. im also trying to write some sort of whatever that will show other users on my website and add them somehow..... i know it sounds complicated or doesnt make any sense, but in my head it does.......

What a fucking genious concept...

[quote]im also trying to write some sort of whatever that will show other users on my website and add them somehow.....[/quote]

Uh-huh.

yeah yeah, it wont be an easy process, but it can and will be done my friends. =D

Heres a very popular c++ client (Direct Conect ++)
source
http://www.dcplusplus.com