Do it online. I've used them for over 10 years (the last 8 or so on macs) and its great

And don't ask 100 boring questions. Something as simple as, "write a function in C to reverse the characters in a string," can be surprisingly revealing.

Excellent point. I believe I've read that making an omelet is a good test of a young chef (one that comes without reputation) that demonstrates technique, skill and work habits.