Three Ring is a free app for Android or iOS that allows teachers to quickly digitize and organize student work into portfolios. You use the app to create the digital portfolio (take a picture) and then the photos are uploaded to the Three Ring site where you can organize the student work, create digital portfolios, share work and examples, and even use it for formative assessment. You can even tag the photos before you upload for easier organization.
This is a great resource for teachers to use to collect and organize student work.
Google Play Android Market: https://play.google.com/store/apps/details?id=com.threering.threering
Apple App Store: http://itunes.apple.com/us/app/three-ring/id504311049
Android for Education resources and apps
Android Smartphone and Apps I use as an educator
Using Evernote for ePortfolios - great idea
OrangeBook - easily create online portfolios of student work