The development of solid state photon detectors has been in constant progress these recent years. In particular, silicon-based matrices of Geiger avalanche diodes, also known as SiPMs have been much investigated for their single photon sensitivity as well as their other interesting properties. They are successfully applied or studied in applications where the highest possible photon detection efficiency is needed (RICH, DIRC, IAC, neutrino detectors) or in experiments where a large dynamic range is mandatory (HEP calorimeters, PET, scintillator readout). The latest developments of solid state photon detectors are reviewed as well as their applications in High Energy Physics, Astro Physics and Medical Imaging.