Just bought new Arduino Leonardo board from Akihabara. So, I just did unboxing video and testing it's special HID(Human Interface Device) function with buttons mouse example. Let's take a look ...
Hardware:
Arduino Leonardo board
5x Push switches
5x 10K Ohm resistors
Breadboard and a lot of wires
Detail
1. Wiring push buttons with Arduino Leonardo as you can see in the image below.(Image from Arduino's official website)
2. Download test program into the Arduino board by run the Arduino IDE and select Arduino Leonardo first then choose File > Examples > 09. USB > Mouse > ButtonMouseControl
3. After download program, now you can control you PC with your push buttons. Have Fun :)