http://www.particlezoo.net/
The site is extremely educational (and also adorable) as once you click on these little plushy particle toys, you get some information about them. The only criticism I would make is that it doesn't feature beta plus decay, where a proton turns into a neutron while releasing a positron and an electron-neutrino.
Anyway, this site is particularly helpful for me as I'm going to CERN on the 26th!
