Dunning has hosted Skeptoid, a weekly podcast, since 2006 dedicated “to furthering knowledge by blasting away the widespread pseudosciences that infect popular culture, and replacing them with way cooler reality.” Skeptoid has been the recipient of several podcast awards, including the Parsec Award. Dunning created the Skeptoid.org video series, inFact, and The Feeding Tube. Dunning has also produced two educational films on the subject of critical thinking, Here be Dragons in 2008, and Principles of Curiosity in 2017.

Dunning also writes articles for Skepticblog.org, published by The Skeptics Society. is a member of the National Association of Science Writers, and “Chancellor” of the non-accredited “Thunderwood College”, a parody of unaccredited institutions of higher learning which offer “degrees” in a variety of subjects.

Dunning co-founded Buylink in 1996, a business-to-business service provider, and served at the company until 2002. He later became eBay’s second biggest affiliate marketer, but has since been convicted of wire fraud through a cookie stuffing scheme. In August 2014, he was sentenced to 15 months in prison, followed by three years of supervised release for wire fraud.