Randall Munroe of xkcd, with the help of a friend who is senior reactor operator, puts radiation dose in perspective:
I’m not an expert in radiation and I’m sure I’ve got a lot of mistakes in here, but there’s so much wild misinformation out there that I figured a broad comparison of different types of dosages might be good anyway. I don’t include too much about the Fukushima reactor because the situation seems to be changing by the hour, but I hope the chart provides some helpful context.
Start at the top left (sleeping next someone), to the right, and then down (standing next to the Chernobyl reactor core after explosion and meltdown) for increasing levels of radiation and warnings.
Really informative. See full version here.