The notion of a free group action on a $C^\ast$-algebra provides a natural framework for noncommutative principal bundles which are not only of purely mathematical interest on their own. As a matter of fact, noncommutative principal bundles become also more and more prevalent in applications to geometry and physics. In this talk we discuss free group actions on $C^\ast$-algebras. In particular, we explain how to classify these actions, with an emphasis on the compact abelian case. If time allows, we further present some applications and open problems.