Note: You are currently viewing documentation for Moodle 2.3. Up-to-date documentation for the latest stable version is available here: Mahara portfolio.
From the Mahara web site:
"Mahara is an open source e-portfolio, weblog, resume builder and social networking system, connecting users and creating online learner communities. Mahara is designed to provide users with the tools to demonstrate their life-long learning, skills and development over time to selected audiences."
It has close links with Moodle. There is a built in single sign on facility called Mahoodle. Future versions of Moodle will have even closer ties as the Mahara Portfolio Plugin development progresses.