Two new projects on nxtprograms.com show how you can have some fun with a simple 1-button remote control using a simple touch sensor on a wire. With a little programming, you can get the single button to control driving, turning, and the use of an attachment.
The 1-Button Remote Control project shows a simple way to control driving and turning with one button.
And the Hammer Car project shows how you can control an attachment in addition to the driving and turning, still with only the one button. This fun little robot looks like something out of a cartoon, but I'm not sure where I am remembering (imagining?) this from.