Online book about visual design for multimedia. The content is a bit old (originally written in 1996), but the principles of layout and color are still relevant.
Wired Campus: Electronic Portfolios: a Path to the Future of Learning - Chronicle.com
Argument for the use of electronic portfolios as a more student-centered assessment of learning
If we truly want to advance from a focus on teaching to a focus on student learning, then a strategy involving something like electronic student portfolios, or ePortfolios, is essential.
On Implementing Web-Based Electronic Portfolios (pdf)
2002 Educause article about using online portfolios. Some of the technical details are dated, but the checklist of "critical factors for successful implementation" is still a good resource
Researching Electronic Portfolios and Learner Engagement (pdf)
Whitepaper on electronic portfolios providing a background on the theory and research. Motivation, engagement, storytelling, and tools are also covered.
How To Create ePortfolios with GoogleApps (eportfolios)
Helen Barrett calls Google Apps the "best free Web 2.0 tool for maintaining an online personal learning environment" that can be used for eportfolios and assessment.
The Bamboo Project Blog: Using Del.icio.us to Create an Easy, Always Updated Online Portfolio
If you are already posting your work online, use a social bookmarking tool like del.icio.us to collect everything in one place. As you create more work, just bookmark it and tag it to update your portfolio.