I have recently heard about http://koding.com. This is a free service for developers, and gives you a virtual Linux machine that can be controlled from within the web browser. You can of course pay for more RAM and a machine that stays on.

I am wondering if this could be an alternative to my workstation01.solidcharity.com: https://wiki.openpetra.org/index.php/Hosted_development_workstation

You can actually install Mono on koding.com, and Postgresql as well.
Unfortunately, the IDE is not very powerful, compared to MonoDevelop on workstation01.solidcharity.com, which is a full Ubuntu Desktop.

You can actually connect via SSH to your Koding.com virtual machine, so it might be worth trying if X2Go also works. But I am not sure if the 1GB RAM limit in the free version will allow work that is fun...

13 days later

ok, so I have setup lxde and x2goserver on the Koding machine today.
You need to login to SSH with a key, so you need to put your public key in .ssh/authorized_keys.

Important: when you follow https://wiki.openpetra.org/index.php/Setting_up_the_hosted_developer_workstation, make sure you don't install the full lxde, because that takes too much space of the 3 GB diskspace in the free subscription plan.
Use apt-get install lxde-core instead!