Http://www.howstuffworks.com - This site is way cool - it tells you how and why stuff works. Once you get to this site you won't want to leave. Amaze your friends with all the knowledge you'll get from this site.
Recreation
Http://www.snow.com - There's no place to ski like Colorado! This site give you a great update on conditions so you know when to play hooky from work! Just don't get sunburned!