I downloaded the PaperPort notes app by Nuance yesterday and am using it on my iPad. It offers a variety of ways to enter notes quickly, including voice recognition, using a keyboard or handwriting. You can also annotate. I'm using the voice-recognition mostly and am very pleased with its efficient way of taking short notes during the day.
It's easy to create new pages to separate notes by different topics. For example I made a to do list, a page of reading notes, and some notes while I was on a phone conversation. The dictation was accurate, quick and it was easy to correct the few mistakes I ran into.
The app was free and I recommend it to anyone looking for a 24/7 assistant.