Hamachi is an interesting idea - it's main appliance seems to be playing pirated games across the internet, though >_<
Depending on how you need to share files, and how big they are, there's various options. I wouldn't use the "\\computername\share" way across the internet, even with an encrypted VPN connection, since SMB/CIFS isn't the world's fastest nor most reliable protocol.
If only one person needs to make files available for a few other people to download, a personal webserver just serving a folder, is very easy to set up.
If multiple people need to manage files, setting up some ftp might be the best option.
If you need to distirbute some really large files, look into torrents - µTorrent has an easy-to-use built-in "mini tracker".