Getestet habe ich die Software nicht, aber die Features klingen mehr als vielversprechend.
Der folgende Text von der Homepage ist zwar englisch, aber so einfach gehalten, dass man ihn auch ohne grosse Kenntnisse verstehen kann.

What it is
With Hamachi you can organize two or more computers with an Internet access into their own virtual network for a direct secure communication.

Hamachi is fast, secure and simple. It is also free.

What's in it for me
Think - LAN over the Internet.

Think - Zero-configuration VPN.

Think - Secure peer-to-peer.

Play LAN games. Access computers remotely. Use Windows File Sharing. Run private Web or FTP servers. Communicate directly. Stay connected.

Hamachi is a zero-configuration virtual private networking application with an open security architecture and NAT-to-NAT traversal capabilities.

Hamachi is the first application to mix seemingly unrelated networking technologies in one powerful package to deliver an unprecedented level of peer-to-peer connectivity. More ...

Hamachi is secure. All Hamachi communications are encrypted and authenticated with industry-standard algorithms and protocols. Nobody will be able to see what two Hamachi peers are talking about. Not even us.

However what is equally important - Hamachi security architecture is completely open meaning that its detailed description is available for the review to anyone interested. More ...

Ease of Use
A special effort went into designing and polishing Hamachi user interface. The result is sleek, simple and intuitive, while still very much functional. Everything you need, nothing you don't.

Hamachi software contains no spyware, bannerware or any other -ware unrelated to its purpose. And it never will.

Hamachi is currently available for Windows 2000/XP only. Linux version is in development.

Latest release
Hamachi for Windows
Released: May 8, 2005
Size: 630KB