Its pretty easy to get the fan out of an old desktop computer. Here are some cool things you can make out of those computer fans:

1) Richard Ebbole shows how to convert a fan into a wind electrical generatorwindfan1.jpg

2) Lowell Chicote converts a fan into a baby mobile baby mobile1.jpg

3) Lahiru Wickramathilaka takes a fan, plastic box and ice cubes to make a simple air conditioneraircon1.jpg