With the increasing use of team teaching and agile classrooms, teachers are now looking for Apps that will assist them in assessing the learning of their students while mobile around the classroom.
One App that is useful for gathering anecdotal evidence is Evernote.
Teachers can make notes, take photos and record audio of the work that students are doing. You can then tag each note for easy searching later. So if you are doing your half yearly reports and want to look back at all learning achieved by students in your Yr 3 literacy group you can if you have tagged it that way. A neat feature is Evernote's ability to read the text in any of your images and make the words searchable.
The other excellent feature of Evernote is the ability to share evernote notes, so if you are team teaching you can share your notes on particular students with your colleagues very easily. Also once you have set up an account on Evernote you can use it across all your device platforms: iPhone, Macs, PCs, Web.
The free version of Evernote is more than capable of meeting most peoples needs. But if you want more you can go to the priced version. See the Evernote website for more information.
If you would like an App that could give you a more structured way of assessing your students there is a very useful list of Assessment Apps at the Apps in Education blog - Assessment Apps by Vicki Windham.