Nikon Europe has a series of free online tutorials which give more information on using various Nikon camera models.
The 'Digitutors' provide basic camera knowledge as well as useful techniques and tips on how to take better images with your Nikon kit.
To view a Digitutor simply find the camera model you have and click on its image. After doing so the specific Digitutor will open and various navigation options will become available. Navigate to various tutorials and tips which are presented in both text as well as video format.