On the right of the homepage (raspberrypi.org) you can find some links to different suppliers.
- A raspberry pi (I would def go for the B model)
- A power supply (1A 5V). These are often sold by the suppliers mentioned above. He might already have one if he owns a tablet or recent android phone.
- An SD card (8gb or greater)
- HDMI cable (he might already have one to connect his laptop/pc to a tv)
- Keyboard / mouse that connects through USB.
- The camera module is a very cool addon.
- A case
For more info: http://www.raspberrypi.org/faqs