Are you looking for a digital portfolio tool? Something that will allow you to save a digital copy of your students' work? Evernote allows you to capture images, import pdfs, or save any other type of media to an online account accessible via PC, Mac, iOS, Android, or tablet device.

My Thoughts:

I used Evernote a bit during the past couple years, most especially when capturing student work on whiteboards. With an iOS or Android app, you can snap pictures and quickly upload and tag with student names, the subject, standards, or any other relevant information.

Need help getting started? Here's a step-by-step tutorial: link.
Here is a post by a second grade teacher on how he uses Evernote in his classroom: link.
If you're interested in emailing media to your Evernote account, here is a tutorial: link.