A very simplified way to describe the difference between spirituality and religion, may be to say that spirituality points to and reflects the direct experience, while religion is an institutionalized version of the same – typically with an emphasis on guidelines for behavior.
Spirituality has to do with coming to the “local” Absolute – a.k.a. the Witness, space & awareness, formless unborn, function of experiencing, and to Big Mind – that which embraces the Absolute and Relative. It has to do with the landscape we find when we enter this territory, and how we each describe it influenced by culture, the language and terminology available to us, and personal flavor.
Religion has to do with how we function when we are exclusively identified with the small self. As there is a strong tendency to be identified with the habitual processes of the small self, there is naturally an emphasis on guidelines of behavior on this level. This is necessary to reduce the expression of some of the most destructive behavior.
We can also say that spirituality is esoteric, while religion is exoteric.
To oversimplify further, we can say that there seems to be a tendency for religion to be found on the first tier in Spiral Dynamics terminology. Today’s spirituality seem to be more at home at the second tier, and also more aligned with second tier science.