Shoutbox

Remote Desktop comes with Windows (XP Professional and Vista Business or better) and will give you the best possible performance for your connection speed.  Everything else is slower. 

The main difference between RDC and VNC is Remote Desktop won't let you shadow a local session (except on appropriately configured Windows server), so it's not very useful for helping someone remotely (for that Microsoft offers Remote Assistance).  There is no file transfer and remote printing is a kludge often difficult to make work.  However, if you don't need those things, RDC is your best choice.

As already mentioned by others, there are several VNC derivatives offering different features.  Some include remote printing and file transfer, though I haven't tested those features with any of them.

Finally, logmein.com, which is a combination of software and service, might appeal to those wanting to remotely access their computer over the Internet and having a hard time with dynamic IP changes and port forwarding.

In the old days, before all of the above, there was PC Anywhere.  There still is and it probably has some nice features, but I haven't looked at it in ages and have a hard time imagining what it could have that the free solutions don't, which would make it worth $200.