As a contractor and part of LDC I have multiple clients on the go at once, one of the problems with that is sometimes their needs overlap or one has a crisis when your on site with another, mostly you can just explain to the client your on site with, not bill for 30mins and go stand in a stairwell to talk them thought it, however often it is far quicker to just log in to a remote server and fix the problem directly.
Quite reasonably clients firewalls don’t normally allow this kind of behaviour and block most of the ports you need to fix such things (SSH, RDP and NOTES), the first response would be to just use a 3G card (and indeed I have one that works rather well and has let me fix client issues in the strangest locations ) but at large clients I always seem to be stuck in a basement or some other no-signal zone.
This preamble is by way of introduction/justification to a private VPN service I am now using, I had a good look round before picking one, needing it to both support on Linux AND not be one designed for anonymous P2P (I DO NOT want a client thinking I am using P2P on there network), the one I picked is http://www.witopia.net/ who provide a very quick professional service with good support (I waited 15 mins for a support responses) and have a great wiki http://wiki.witopia.net/wiki/Main_Page
If you want it for the same usage as me then you want a certain configuration else your not going to get out of the firewalls
1) You will need the “personalVPN - SSL (openVPN) ” product http://www.witopia.net/index.php/products/
2) You will need to swap to alternative ports (443) http://wiki.witopia.net/wiki/Alternate_Ports
3) If your on Linux (ubuntu 10.04 + ) and have followed the wiki instructions, you will also need to alter the advanced setting on the VPN configuration as below (this is not on the wiki)
solves a lot of problems for me.