[link|http://www.radmin.com/default.html|RAdmin] is a tool we use, particularly for beyond-the-LAN access to systems, as it integrates an encrypted session with the remote access. It also autodetects connection speed and sets connection properties (largely image compression) accordingly. It only runs under Windows. Cost is $35 per remote/locale tuple, with bulk licensing possible. By "remote/local", I mean that one license is good for one local and one remote installation. This gets a bit squeeky in a star-model, where one workstation provides remote access to many desktops.

All this can be accomplished with TightVNC, though with more work and additional alternatives (eg: an ssh client/server).