I learned today, from a company with about 20 employees, of a solution for people who have Microsoft's XP Professional operating system on their PCs: Remote Desktop. The nice thing is that you can connect to the computer--and apparently a host--from not only a laptop or a desktop, but also from a Pocket PC (a handheld device with Microsoft's made-for-handheld operating system) or a smart phone. The downside is that you, apparently, must have XP.
CNET's Robert Vamosi did a nice job of reviewing some of the other solutions, as well.