@FreyjaW: I use excel. I resize the cells so they're squares and every square represents one square foot. I then carefully measured everything out and made a map. In every square I plant I put a number, and then I have a table where I can reference the number to what I planted. When a new year rolls around I tend to just make a new tab and copy the layout. Occasionally, I'll start a new book. I also use to to keep an inventory of my seeds, used it to design my irrigation layout and tell me how many of what part I needed to by, and to do my research on what I want to plant and then plan my purchases. I've got some other stuff stuffed in there as well. Excel is quite handy.
Click image to zoom