Why is the axle moving when the car is in neutral?
 

97 Camry v6, 5 speed, I just did a timing belt and I started the car, I heard some noise and the right axle is spinning and the car is in neutral. The driver side is not moving but why is the passenger side axle spinning? What would cause this to happen?

if you are up on car stands

this is normal .... the tyres have no weight on them or a load

this is a manual gearbox with a standard differential design
if it was a limited slip diff both wheels would turn