Who isn't watching through the window to see what type of weather it is? The weather is something that affects everyone, everywhere in the world. I find it pretty interesting so I once bought a WS-2300. This weather station records humidity, pressure, temperature, dewpoint, windspeed, windchill, etc. This weather station is connected to an old RaQ2 which is a very low power consuming (web) server. Now it runs Debian instead of the original RaQ OS. Because I can download the data, I can store it in a database (mySQL).
With data being stored every 15 minutes, I have enough information to make interesting graphs. Right now there are more than 30.000 records in the database. Using these graphs I have made a standalone Weather site, right
here.
Note: I've recently moved to another location, and the weatherstation has not been mounted on the roof yet, therefore the weatherstation site is temporarily not working.