I like Evernote. I like how students can record the teacher and take notes at the same time. You can email from it as well. Students in my class have taken pictures of notes that I had up on the board. Also, students can get pictures, articles and many other things off the net, as most web pages let you save it to evernote.
Personally, I like Noteability a little better. The color coding that it offers is what swayed me. Also, Noteability let's you hand write as well as type, and you can change the background colors.