I just submitted a new plugin, the Blog Export portfolio, to the plugins database. It allows students to export items from Moodle such as forum posts and assignment submissions, to their own Moodle blog. This makes it possible to use the Moodle blog as a simple internal portfolio.
It was funded and released to the Moodle community by the British Council TeachingEnglish. It was developed by me. Until it goes live on Moodle.org, you can get it at http://poodll.com/blog-export-portfolio/