I have been using the DocScanner App for iPad for several weeks now. The App allows you to photograph business cards, receipts, and documents and forward them as photographs, PDF copies, or to convert them to text via OCR. Today, during a meeting that I was hosting via GoToMeeting with five attendees, another attendee in the room with me started discussing a document that he had brought to the meeting. Within less than 30 seconds, I was able to scan the document and display it to those in the room and those online. Image quality after scanning for OCR text conversion is equivalent to a black-and-white copy on a medium grade copier.
In summary, DocScanner is a good choice for scanning on the fly.