The most satisfying science sites are ...

I would like to start this off with my two favorites:

http://en.wikipedia.org/wiki/Wikipedia:Featured_articles

and

http://www.sciencedaily.com

Here is one of my fav's:
http://www.newscientist.com/news.ns

And this one:
http://www.physorg.com/

And this:
http://news.bbc.co.uk/2/hi/science/nature/default.stm

In Astronomy:
http://antwrp.gsfc.nasa.gov/apod/astropix.html

And this:
http://www.universetoday.com/

For general science/geekery I like:
www.gadgetopia.com

For my hobby (brewing beer):

www.brewingtechniques.com
www.hbd.org
or www.beertown.org

I'm not sure it falls into the desired category but it's certainly worth the time reading these forums (and posting in them) - http://www.physicsforums.com/