Gamma-ray Observations of Extragalactic Particle Accelerators

With the ground based VERITAS, MAGIC, MILAGRO, and HESS experiments and the upcoming space-borne GLAST observatory, we now have access to a powerful suite of telescopes to probe high-energy particle populations in a wide range of astrophysical systems. In this contribution, I discuss the science topics that can be addressed with observations of high-energy particles accelerated close to supermassive black holes, in normal and starburst galaxies, and by large scale structure formation shocks. Furthermore, I will highlight recent results obtained with ground based gamma-ray telescopes.