Video Chat for Dummies

[Lemur]

Okay, for the last ten years I have studiously avoided the whole world of video chat and video conferencing. However, my parents have retired to a distant state, and they want to video chat with their grandkids, so I am forced to enter this seedy world.

Anybody care to give me a quick primer? What are the best, cheapest (free?) services for hooking up a couple of technophobic grandparents? I've heard of quite a few people using Yahoo! video chat -- does it work? Is it reliable?

What should I be thinking about, what are the pitfalls, and what's the optimum set-up? I'd like to stick with free and/or open-sauce when possible.

Thanks in advance for your guidance and wisdom.