A short, user-oriented description to the HiPE compiler's features appears in:
(and might have been afraid to ask)
Here's an old introduction to the HiPE project.
For easier analysis, transformation and compilation of of Erlang programs, we have constructed a core language for Erlang. More information (including the latest version of the specification) is available on the Core Erlang page.
We also have some pages with help on hacking (for HiPE members, compiler project students, etc.).