ERD of information_schema / system catalog?

Hi,

Did a little googling but didn't come up with much - does anyone know
if someone made an ERD of either the information_schema or system
catalog (pg_) tables for postgres 8?

Something similar to this for MySQL 5 would be ideal:

http://www.xcdsql.org/MySQL/information_schema/5.1/MySQL_5_1_INFORMATION_SCHEMA.html

Thanks,

Josh