Andrew Lathrop developed a way to make a cheap digital camera's CCD sensor detect radiation.
There are plenty of DIY camera mods out there, but this is the first time we have ever seen anyone create their own radiation detector. Lathrop's technique involves covering a couple of layers of scintillator in a reflective material, placing them in front of the camera's lens, and then light sealing it to the best of your ability. Scintillators are materials that when hit by radiation, they luminesce. In other words, when hit by invisible radioactive particles they emit visible light. In this setup they're the only light source, and manage to show how much radiation is being emitted down to a 100 banana dose.
Lathrop describes his project as:
I created this inexpensive radiation dosimeter for the people of Japan. Strange that when I sent this to Japanese newspapers it was not printed or commented on.
We were all amazed at the sensitivity of an inexpensive digital camera ccd to beta radiation eqvalent to 100 bananas (+- 1.0 mrem).
I have run the experiment Pyrex dishware with 14 bananas as a source using 10 exposures resulting in 4.7 sigma events. A single photo yielded only a 1.5 sigma not signifacant to write about. I still have a few more experiments to do.
The big problem is that scintillators aren't exactly easy to come by. You can use Pyrex, as mentioned above, but it's notably less efficient. Unless you happen to be working in a lab, the chances of you having any plastic scintillators floating around your workshop is pretty slim.