I'm remembering a classic Scientific American article (1990s, I think) on detecting high energy cosmic rays from the Earth's surface-- which means detecting the rain of debris caused by a high-energy cosmic ray hitting the atmosphere and shattering atoms. That whole article may not be available for free on-line (I haven't looked too hard) but here's something more recent-- the most powerful known cosmic ray particles have the energy of "a fast pitch baseball":
http://www.scientificamerican.com/ar...to-black-holes