If anything you do is somehow related to databases, you absolutely, definitely have to see these videos:

Part 1:http://www.youtube.com/watch?v=40Lnoyv-sXg

Part 2: http://www.youtube.com/watch?v=GbZgnAINjUw

Part 3: http://www.youtube.com/watch?v=y70FmugnhPU

Go the links from Tom Kyte’s blog.