Huffington Post Live has a debate on the economy featuring Gary Johnson, Rocky Anderson, and Reform Party candidate Andre Barnett (on the ballot in Florida). Unfortunately, I have not figured out how to embed it, although other IPR writers are welcome to update the post with the direct video if they can. Otherwise, just follow the link. This is, as far as I know, the first presidential debate with candidates from more than one party at the same time that Gary Johnson has been in.
Free and Equal has a more widely promoted debate coming up October 23 with Johnson, Anderson, Green Party candidate Jill Stein and the Constitution Party’s Virgil Goode.