In reply to The Lemming:
The issue here is not some of the software being mentioned (Microsoft Remote Desktop, VNC or Remote Desktop [Apple]), which will all work, but the firewall setting that would have to be down for these to work natively without being blocked. The usual way around this is to use a third part agent like TeamViewer that uses ports used by standard services (used by the Web) or to set up a VPN on your firewall, but that is complicated to set up on most boxes, and individual at each site.
In our business we have a TeamViewer licence, but even a single seat is getting really expensive now. VNC Connect, Troopmessenger and Logmein are all free. I used VNC connect years ago and it was OK, I have not used the others.
Post edited at 06:40