Glass, being transparent, symbolizes the barrier between ordinary life and the life hereafter and between the physical and spiritual realms. It can also suggest the transparency of truth as we understand it.
Psychological / Emotional Perspective:
To dream of breaking glass is to be breaking through barriers. We are shattering the emotions that keep us trapped and moving into a clearer space where we do not allow barriers to build. Frosted or smoked glass can indicate a desire for privacy, or our obscured view of a particular situation within our lives.
Everyday Material Aspects:
Dreaming of glass indicates the invisible but very tangible barriers we may erect around ourselves in order to protect ourselves from meaningful relationship with other people. They may also represent the barriers that other people put up and also be those aspects of ourselves that we have built up in our own defence.
Also consult the entries for Barrier, Break, Mirror and Reflection as well as Windows in the Buildings entry.