Certainly. There are gun shows all over the place here.
At gun shows in Colorado, if someone without an FFL wants to sell a firearm to someone else without an FFL, they have to go to someone who does have an FFL so the Colorado Bureau of Investigation can do a background check. This usually takes only 15 minutes, but at the height of the post-Sandy Hook buying frenzy it was taking almost 3 weeks to be approved...a de facto waiting period.