In the spring of 2009 I got my current digital camera, a Nikon D90. It is an excellent camera, with 12 megapixel resolution and plenty of functions.
In order to fully be able to use it, I looked around online and found a number of great pages with information and tips for this camera. I want to share them here, for any other D90 owner that happens to find this page.

Ken Rockwell's Nikon D90 User's Guide is fairly easy to read (easier tho understand that the Nikon D90 manual) and have plenty of good tips.

Nikon Digitutor is the official Nikon online tutoring site, with videos explaining the camera and it's functions.