1. A tour of PostgreSQL by Tom Lane
  2. Steps in building and running PostgreSQL
  3. Setting up PostgreSQL in Eclipse
  4. PostgreSQL internals through pictures
  5. An Introduction to Hacking PostgreSQL by Neil Conway and Gavin Sherry
  6. PostgreSQL 9 internals documentation at postgresql.org (gives quite a bit of information)
  7. Bruce Momjian's presentations on PostgreSQL internals
  8. PostgreSQL 9.1.2 source tree
  9. postgresql-9.1.2.tar.gz (for you to download)
  10. A talk from CS 631 a few years back
  11. Useful PostgreSQL links