List of required components:
1. Raspberry Pi Model B for internet access
2. Powered USB hub
3. Power supply with 3-4A
4. (Optional) USB Wi-Fi dongle. Guides on setting up the Wi-Fi dongle are plentiful. You can do it with command line via SSH or from the GUI.
Step 1: Hooking up the Raspberry Pi
Discard the power adapter that comes with the powered USB Hub if it supplies less than 3A. You need 700mA for the Pi and 500mA for each hard drive you connected.
Connect the USB Wi-Fi dongle to the Raspberry Pi.
Connect the USB output cable from the hub to the Pi. This should also power the Pi, so no need for a mini USB cable.
Connect the hard drives to the hub,
Power on the Pi. Powering Pi before plugging in USB components may restart Raspberry Pi.