I am using Evernote on an increasing basis.
It also is a great tool for file sharing, and I love that it syncs on all my devices.
The more I use it, the more I discover great uses for it.
I do not go to a conference, a workshop or a seminar without using it.
It is extremely easy to take photos with it while taking lectures, and to add on from there.
I get more from my notes than only relying on the PowerPoint afterwards.
With the most recent New Librarianship MOOC, a fellow student shared her notes, and I could follow which worked great. As soon as she updated her notes on a new module, it was available on my device as well. File sharing is extremely easy with it!
I did the Social Media in Libraries presentation with notes and research that I compiled into a Notebook on Evernote.
This is one of my favourite apps!
I must also add that I like how it has changed with the iOS 7 update. Everything is accessible from the home page!