I have yet to find the perfect digital portfolio app that I think I would use exclusively in a visual arts class. Some apps can be used as graphic portfolios or as beautiful sketchbooks, others are great at sharing. Not all of the apps available are great at all of these things. I have spent a heap of time trying to find one and would be more than happy for someone to send me the name of ones they are using successfully. Having said that, the following are apps that I would consider using as eportfolios:

Evernote: FREE 
Evernote is an easy-to-use, free app that helps you remember everything across all of the devices you use. Stay organized, save your ideas and improve productivity. Evernote lets you take notes, capture photos, create to-do lists, record voice reminders--and makes these notes completely searchable, whether you are at home, at work, or on the go.