I use pc/anywhere. I believe this may have been dropped by Symantec but it works well. It even works over GPRS - if you have patience and if somebody else is paying the GSM bill
The thing to watch with any remote control program is that port sniffers will soon find the port it's on and will hit it with a dictionary attack, or a simple DOS attack. So, most serious users do remote access over a VPN, or at least switch off the host end when not required.