SCIENCE:
Astronomy Picture of the Day
If you have an RSS feeder or other service that lets you subscribe to this site, I highly recommend it.

Otherwise, you can click on the site daily, but it's easy to forget. Some of the pics on here are fantastic.
National Hurricane Center
This is the official site for the National Hurricane Center, part of NOAA (National Oceanic and Atmospheric Administration).  It lets you subscribe to RSS feeds for individual storms, and see archives of past storms.
Aurora Borealis
This site shows a near-realtime depiction of where the aurora is diectly overhead. The aurora, or Northern Lights, can also be viewed at an angle from quite a ways further south, and occasionally, during periods of very high solar flare activity, as far south as Amarillo, just above the horizon.
Space.com
Space.com has some great stuff on it.  My personal favorite is Starry Night Online.  Here you can enter your zip code, time of night, and see what that the night sky will look like to the north, east, south, and west, as well as straight overhead.
Main Website Page