The situation here in Tokyo is becoming very grave indeed. I managed to get quite a lot of food and drink today but I couldn't get batteries, lights, candles or medical supplies. I can't imagine supermarkets and chemists reopening in the next few days, but just in case I'll go out tomorrow to see if I can get some iodine tablets and other medicines.
I'm about 220 km from Fukushima where the reactors are located which sounds quite far but really isn't when you are considering the movement of radioactive dust and water. Although I have a few hand tools and some basic materials I don't think it would be possible to seal my house against fallout. The nearest DIY store is about a hour on foot, and is very unlikely to be open.
Here are a couple of practical links for people in the Kanto area of Japan.
How to build a fallout meter:
Very practical book on dealing with aftereffects of nuclear accidents:
Another book on surviving nuclear accidents is "Life After Doomsday". It's available on BitTorrent or eBook websites like http://www.ebookee.com
Here is some info on previous cover-ups of nuclear disasters in Japan: