More information on portfolios:

http://billcarozza.com/category/digital-portfolios/  

How to grade from Scholastic Administrator:
http://www.scholastic.com/content/collateral_resources/pdf/a/administrator_aug05_pdfs_Grading_EPortfolios.pdf

Before beginning things to consider:
http://www.scholastic.com/content/collateral_resources/pdf/a/administrator_aug05_pdfs_questions.pdf