Web Server Plugin
 

Is there any plugin that would let me call up a document from a web server, allow me to edit it, and then save it back to the server? I'm not sure exactly how to explain it, but I think that says enough.

The way you describe it: No, that's not possible.

But this is how I read the question:
A plugin (client-side) that can edit documents (server-side).

It is possible to do this, but only on the server.

That's where authentication takes place and is decided who can do what (upload/download among other things). In short: the server decides which client(s) (user) is allowed to do certain tasks.

The plugin you ask for would be a great tool for hackers :)

Re: Web Server Plugin
 

What kind of document are we talking about, plain text, html or something? We have a program here that allows users to login and edit html pages in real time, so it is possible, but just depends on the type of files and such.

Ours works by placing tags within the html files, so they can only edit parts of the files.

I am sure something similiar could be made using some CGI, perl or something along those lines..

Are you looking for something like WebDAV?

It is called Konqueror. If the server uses SSH you can login through the fish kio-slave and edit files through KWrite for example.

You don't have to use Konqueror, you can use IE5 and up.
All you have to do is install the webdav module for your apache server - libapache-mod-dav to be exact.
add a few lines to your apache conf file and your good to go.
you can open your site as a "web folder" and then edit to your hearts content.