I was just looking through the table Mitch put up under the 'Miscellaneous' Nuclear link, and I was kind of shocked by how many so called stable elements have a large proportion of radioactive isotopes. Re-187 is 62.6% of all naturally occuring Rhenium, and is a radioactive isotope with a half-life of 5.0x1010 years. Indium, however, is 95.7% In-115 which is radioactive! It's got a half-life of 4.4x1014 years though. I did some calculations, and that comes out to an activity level of around 0.36 Bq per gram of pure Indium metal. I don't know if there is anything out there that can even detect that. This is the type of data that I would love to show people and watch their reaction when they see that certain things which aren't thought of as radioactive actually are. Then they can realize that just because something is radioactive doesn't mean that it's dangerous.