There are many companies that specialize in selling modules and add-ons that can be used with computers and devices, such as Raspberry Pi, that are aimed at the hobbyist. Some of them are as follows:
- Adafruit Industries: http://www.adafruit.com
- SparkFun Electronics: http://www.sparkfun.com
- Mouser Electronics: http://www.mouser.com
- Banggood: http://www.banggood.com
- DealExtreme: http://dx.com
- Pimoroni: http://shop.pimoroni.com
- Pi Supply: http://www.pi-supply.com
- PiBorg: http://www.piborg.com
- Hobbyking: http://www.hobbyking.com
- ModMyPi: http://www.modmypi.com
- Quick2Wire: http://quick2wire.com
- GeekOnFire: http://www.geekonfire.com
- Ciseco: http://shop.ciseco.co.uk
You can also take a look at my ...