I liked Ger's comment that a portfolio is a redundant feature as a learning tool if you are using Moodle effectively. That is true at the course level, but many institutions (especially U.S. based) have to be concerned with program and institution level assessment. E-portfolios are a great way to facilitate that assessment. Ideally, the site administrator would be able to create a portfolio template with each of the institutions instructional goals or learning outcomes. Students would then be able to upload files to fulfill those outcomes (or simply link to an assignment, quiz, forum, or journal from a class that would demonstrate that they have completed or met the requirement). Then, faculty/administrators would be able to pull all responses for a given category of student for any of the outcomes, rate them, and have assessment data about institutional effectiveness in a given area. I am currently attending an accreditation meeting in the mid-west portion of the u.s.a. and can tell you that this is what the majority of the sessions are focusing on (assessment that is) and that this type of module would be amazingly helpful.
Unfortunately, I'm not a php developer, so I can't make this module happen, but I would love to be involved in the development of it. Perhaps the first step would be simply providing the module that students can add their material to. Once that is complete, work can begin on the faculty assessment aspect of it that would draw info from all of the student portfolio and remove the personal student information (that would help protect privacy and bias when doing an institutional level assessment).
Let me know if there are any interested developers out there to work on something like this. (I may even be able to swing some funding, although it would probably be minor).
p.s. see the rose-hulman project for an example of the type of system I'm thinking of: