It depends on how artistic you are but often a little drawing can speak a thousand words. Usually that means drawing it onto a piece of paper, scanning it and embedding it into a Word document or hopelessly trying to doodle something with your mouse. But with this simple Iogear Digital Scribe Pen and USB Receiver you can just draw or write on a piece of paper and it automatically shows on your screen. You clip any kind of paper in the USB receiver which tracks the pen's movement. The included software even has handwriting recognition so you can write a text and it automatically transfers to digital (keyboard typed) text. As you can see in the image below it's very compact which makes it a great laptop accessory.
Amazon sells the USB pen and receiver for $ 60,-.