If your are like me which I am guessing you are, then ever since you got into doing stuff with arduino you have wanted to make your own arduino board. You may be surprised to find out that making the prototyping board is actually very easy, and can have several advantages over using the commercially sold board. For one thing, All the components together cost a little over 15 US dollars as opposed to the $30 that the Uno board sells for. second, you may not actually want a board, but may simply want the atmega chip as the heart of the project, like if you are making a synthesizer or even a robot. In that case, you can just attach the hardware necessary to use the chip, and solder to the pins you need to use without needing the board. Another advantage is making shields. You have probably noticed that digital pins 7 and 8 are not the standard distance apart, which makes it difficult to make your own custom shields without paying the $15 dollars for a protoshield every time you make one. But if you make your own board on perfboard, the headers will be the standard distance apart and you can make your own shields with ease. Also, you may need to permanently add the board to your project, and for that you may not want to use the more expensive arduino boards. This board however is half the price, and easy to add to custom projects.
The only down side is that some parts of the arduino are kind of hard to build on perfboard. Most notably the Serial to usb adapter chip, which allows the microcontroller to interface with the computer through usb. You could use a good old RS232 jack, but they are not on a lot of newer computers. So to program your homemade board you will either need a break out board which does have the chip (get one here: http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2117341_-1
), or an arduino Uno or clone board to program the chip ( I used the former.)
Either way it is a fun and informative project.