Myles Power is a skeptical activist who has produced a series of Youtube videos on his powerm1985 channel investigating and talking about various skeptical subjects; from 9/11 truthers to religious absurdities and GMO. His videos are accessible and well produced, and are an excellent grounding in some of the main talking points in skepticism.
A Chemist by profession, Myles has spent many years not only producing videos, but has hosted podcasts and written extensively on these subjects.
He has twice spoken for us, once on AIDS denialism and once on GMOs. Go check out his videos if you're new to skepticism. They are a great place to start.