Which free VPN providers support Ubuntu?

Try the Bestfreevpn. This is their link also read this for more info

Another vpn provider's services that work on Ubuntu are those by a company called Securitykiss. However, the free user is only allowed 300 mb per day, but this may be enough if you are using it in a cyber cafe, for example, to secure your connection.

The setup of Securitykiss requires much more effort than bestfreevpn, so it is up to you which service you choose. You can either use PPTP (instructions here) or openvpn (instructions here).

Before you can follow either of these sets of instructions, however, you need to get a configuration generated for Linux based systems from here and then log on to the client area here and download your package which contains further configuration details.

Securitykiss takes a bit to setup and is limited to 300mb for the free user, but is an example of a 'free' vpn service, of which there are very few 'free' examples out there.

I have just been experimenting with it and wanted to bring it to the attention of the community, as it does work successfully on Ubuntu and the instructions on the site are tailored to Ubuntu so I thought it might be of interest.

If you mean VPN Clients check this:

PPTP (Microsoft VPN)

sudo apt-get install network-manager-pptp

Cisco VPN

sudo apt-get install network-manager-vpnc

OpenVPN

sudo apt-get install network-manager-openvpn

If you mean VPN Servers check this:

OpenVPN

https://help.ubuntu.com/community/OpenVPN

PoPToP

http://cviorel.easyblog.ro/2009/02/09/how-to-set-up-a-vpn-server-on-ubuntu/