The Astronomy Picture of the Day is the website run by Robert Nemiroff and Jerry Bonnell. They're a couple of awesome space geeks, and they both have a bunch of material other than this site that's worthy of your eyeball time.
The site has a calendar with thumbnails of all the past APODs... surf and learn. It's guaranteed to consume at least three (3) hours of your net time, if you're into this kind of thing.
Find APOD @: http://apod.nasa.gov/apod/astropix.html