  We generalize the concept of coherent states, traditionally defined as
special families of vectors on Hilbert spaces, to Hilbert modules. We show that
Hilbert modules over $C^*$-algebras are the natural settings for a
generalization of coherent states defined on Hilbert spaces. We consider those
Hilbert $C^*$-modules which have a natural left action from another
$C^*$-algebra say, $\mathcal A$. The coherent states are well defined in this
case and they behave well with respect to the left action by $\mathcal A$.
Certain classical objects like the Cuntz algebra are related to specific
examples of coherent states. Finally we show that coherent states on modules
give rise to a completely positive kernel between two $C^*$-algebras, in
complete analogy to the Hilbert space situation. Related to this there is a
dilation result for positive operator valued measures, in the sense of Naimark.
A number of examples are worked out to illustrate the theory.
