Simple Desktop Remote
Simple Desktop Remote allows you to remotely control any computer (Windows, Linux, MacOS X, BSD, Solaris ...). It is very easy to use and by opening one port on your firewall you can control your home computer from anywhere.

TightVNC Remote Control
TightVNC is a FREE remote control software package. With TightVNC, you can see the desktop of a remote machine and control it with your local mouse and keyboard, just like you would do it sitting in the front of that computer.

Log Me In
LogMeIn Free allows you to control on computer per account from anywhere on the web. Basically, you can be sitting at home and control your office computer. With the Free account (single email address) you can control one computer. If you have more than one computer you want to control setup another account using a different email address.

The Pro version adds files transfer and remote printing. It costs $69.95 per year ($5.83 p/mo) and drops from there if you add more PC's. This is probably the cheapest product on the market.

Commercial

GoToMyPC
GoToMyPC is probably the most well know remote control software. It costs $19.95 per month for one PC and offers compete remote control.

RemotePC
RemotePC costs $9.95 per month and allows you to remotely control up to 3 computers. They also give you 5GB of online storage space.

Dameware
DameWare Development's powerful remote administration software provides you with "out-of-the-box" ROI, and offers many features boasted by larger vendors at a fraction of the price tag. It is also considered by many industry insiders as the "swiss army knife" of remote administration tools, and should be a part of any administrator's arsenal.