Well, I recently bought a Geiger Counter. If you want to look at the specs, click here. It counts Alpha, Beta and Gamma radiation.
I have decided to measure, over the course of several days and weeks, the counts per minute around me. I will do a count outside (in my driveway) with the device pointing to the sky, and also indoors. Obviously the readings are somewhat random, so I'll take 5 readings and average them. Outside has a CPM of about 20 at the moment.
I also decided to take readings of various household objects, just for fun. One thing I was somewhat concerned about was the granite benchtop of our new kitchen, as I had heard of people with highly radioactive slabs. Ours does produce a higher count than ambient, about double in fact, but I am not worried about that. It's about the same as a common housebrick, with a CPM of around 40.
The only source of radiactivity in the house, that I know of, is in a smoke alarm. I had a spare one, so I took it apart just enough to expose the metal housing of the radioactive unit. That is, I removed the plastic cover only. There is a sticker that says it has a tiny piece of Americium in it. A direct reading on this metal housing gave a CPM of over 100. Moving away a few centimeters and taking a reading it dropped off considerably back to background levels. Don't panic about your smoke alarm, it's not going to kill you unless you break it open and eat the contents, and even then I'm not sure it would be a lethal dose. Still, I don't recommend it.
I wonder if the issues in Japan, which are a long way away, will show in my readings. Time will tell, and I'll get back to you on that.