This app is amazing; stand in the center of a room, spin around and take photos of each corner in a room and each side of the doors and the app creates a floor plan. No need to measure, no need to move furniture and no need to draw. You can calibrate the dimensions by measuring one wall of a room.
The app is free for download. The final floor plan is free for non-commercial use (includes a watermark) and $1.10 USD for commercial use (with the watermark removed).