"If your view of portfolios is just something akin to a content management system, don't bother. But if it's the student's personal and continuing presence in an online community of discourse, then you are on to something. " (Stephen Downes, 2004)
Batson (2003) defines an e-portfolio system as "a dynamic Web site that interfaces with a database of student work artifacts". It is, in other words, much like a repository (see also the chapter in this book on institutional repositories) except that it is specifically focussed on products created by students. Portfolio-based learning and evaluation is usually concerned with individual students' creations, but collaborative portfolios do exist. Even where individual products are emphasized, students are often collaboratively involved in commenting on and rating one another's products.
eFolio Minnesota provides a space for all Minnesota residents to set up and maintain a personal e-portfolio.
There is a longish list of other portfolio software systems in Trent Batson's (2003) article (near the end).
The Electronic Portfolio Consortium, or ePortConsortium, is the collaboration of higher education and IT institutions working to define, design, and develop electronic portfolio software environment and management systems.