I'm constantly accessing different computers, but I don't need to get up from my chair to swap PCs. Instead of walking between them, a VNC (virtual network computer) setup lets me log into remote machines that are across the room or around the world. Now I can manage software installations, see if a download is complete, or just troubleshoot from anywhere.

Windows XP Professional, and Vista Business and Ultimate include this functionality, called Remote Desktop. (Lesser SKUs can connect to those operating systems, but they can't host a remote computer.) You can also set up PCs with the open, VNC protocol, using a range of software. But those routines often require port forwarding and other network management. I've shirked that level of network management and sampled LogMeIn, which uses its web server so you don't need to know IP addresses or other networking details. Plus a new, albeit paid, iPhone client [app link] drives it all from anywhere.