Shoutbox

What exactly do you mean? 

If you have set up a VPN for connecting to your home network from outside and want to make sure it works before you need it and discover it doesn't, the only two ways I can imagine are to take your laptop and go somewhere, or to ask someone to test it for you.  You should be able to find someone from this community who can help you with that on IRC, and you can always change the involved passwords and/or certificates later.

To be able to conduct that kind of test yourself, you would need unrestricted remote desktop access to a Windows machine somewhere else (or root shell access to a Unix machine if your type of VPN is supported there), which won't be easy to find.