Question : share document over the web

I need a way to share a word doc, power point and excel documents over 3 different networks.  I cannot FTP on any of the networks.  I don't want to download the file and edit it then have to upload it again.  I want to be able to open it directly and if someone else tries to open it they get a message that it is already open.  Just like sharing over the same network via explorer.

Answer : share document over the web

Not available now, but office web apps should be available in 2010; here's an overview: http://mashable.com/2009/07/13/microsoft-office-2010/