Here are a few resources you can use to help you get to grips with the Raspberry Pi (in no particular order).
Using Python Good tutorials for using Python – we’ll be using this for GCSE
The official Raspberry Pi website – loads of useful information. The forums can get VERY technical. The downloads section is where you find the latest version of Raspian if you need to re-flash the SD card.
Lots of really nice exercises on the OCR website for using the Raspberry Pi.
Scratch official website – tutorials etc. for Scratch.
Info about the Pi-face interface for the Raspberry Pi
Tutorials from the University of Cambridge.