For the last semester I have been using a handy scanning app called Genius Scan. Its a free app, simple to use, and has been really useful. This app allows you to take a poor-quality photo of a document and turn it into something you aren't ashamed to send to a colleague or student. The app has two primary features. First, it automatically detects the shape of your scanned document and ensures that it takes on the correct perspective. For example, when your document inevitably assumes the shape of a parallelogram when photographed at an angle, the app will automatically transform it back into a rectangle. The second feature is that it automatically transforms your scan into black and white text. This means that your photo won't look like a photo at all.
The app is very intuitive to use. It is easy to add multiple pages to a single file. It is also easy to either email your document or save it directly to dropbox. The default file is a PDF, but you can also save as JPEGs.
I've used this app on multiple occasions to scan graded student assignments that I want to return electronically. I've even scanned a few pages of a book to send to a colleague, the though results are not as strong if the book binding causes the pages to curve.