http://www.colorado.edu/philosophy/vstenger/Assuming you'll get lots of pointers to people like James Randi, Michael Shermer etc. Stenger doesn't seem to get as much publicity, but he does great work in the field.
He has degrees in both quantum physics and philosophy, so is pretty much un-bullshitable by the woos coming from either the Fake Science or Fake Philosophy camps.
He absolutely despises the misuse of quantum physics by hucksters like Deepak Chopra, and wrote a great book about it - "Quantum Quackery."
I saw Stenger speak at the Skeptics Society here in Los Angeles. Like Richard Feynmann, he has that great and rare gift for being able to explain very difficult scientific concepts in plain language. When discussing the abuse of quantum physics, he explained stuff like the Double-Slit Experiment so that even I could understand it.
And for all those who claim "science can't disprove the existence of god," Stenger says science can do exactly that.