Logmein is a free application which allows you to connect and remotely control your PC. It's not new, but I'm a new fan having used it while I was away at a conference this week. Happily, it works with Vista, as I was using a Vista laptop at the conference to connect to my Vista box at home.
One thing I learned - the remote access does depend on the remote PC being powered on. It sounds like a no-brainer, but I was on autopilot before I left home and put my PC into hibernate mode. I had to make a phone call home to get it turned on, which wouldn't be possible if you live on your own! So if you intend to use Logmein on the road, make sure you leave your PC turned on!
My one gripe was that if the PC you're trying to access remotely needs to be powered up, there seems to be a delay of a few minutes before that PC shows up as "online" to you at the remote location. Admittedly, I was attempting to access it from a fairly crappy hotel conference room media centre with Vista machines on an unreliable wireless network, so any of those factors may have contributed to slowing down the remote connection!
We wrote up the use of Logmein as a way to provide remote tech support here.