The best website of 2009 has to be www.wolframalpha.com.
It is a search engine, like Google. Unlike Google, it does not search for websites, but rather for data. Type an equation, it displays the result, graph, derivative, integral, series representation and more. Enter a stock symbol and you get market cap, listing price, highs and lows, etc. I asked for the weather in Seattle when Jimmi Hendrix was born - and it delivered! (38° with 88% humidity, in case you're wondering.)
This website has one downside that I can see: It has a hard time interpreting inputs correctly at times, but this is improving.
My favorite use: math homework! I always seem to get stuck on the trig integrals. Wolfram doesn't just give the answer, it also shows the steps to get the answer!
I give it Two Thumbs Up!