This project implements a server side module that adds UUID type to PostgreSQL 8.1. All functions, operators and opclasses from 8.3 are available.
The UUID type support in PostgreSQL 8.1project is a PostgreSQL Community project that is a part of the pgFoundry.
The pgFoundry page for the project is at http://pgfoundry.org/projects/uuid81, where you can find downloads, documentation, bug reports, mailing lists, and a whole lot more.