Any position and its conjugate momentum have commutator [itex]i \hbar[/itex].
It's not just linear position and momentum,
[itex][x,p_{x}]=i\hbar[/itex],
but angular position and (the proper component of) the angular momentum (the component being the one parallel to the axis of rotation),
[itex][\theta,L_{\theta}]=i\hbar[/itex].
Going into a bit more detail:
According to Dirac, one way of getting quantum mechanics from classical mechanics is by substituting the Poisson bracket algebra with i hbar times the corresponding commutator algebra.
[itex][\hat{q_{j}},\hat{p_{j}}] = i \hbar \{q_{j},p_{j}\} = i \hbar[/itex].
Assuming this always works, then the commutator of any generalized coordinate with its conjugate momentum will always be i hbar.