a great webcomic
http://www.userfriendly.org has a 'link of the day' at the bottom of their main page.
their links are faaaannntastic usually (sometimes just okay) but they keep it all archived for those really bored days we all have.
today's is pretty damn cool if i do say so.
http://science.nasa.gov/Realtime/jtrack/3d/JTrack3D.html also, this one was just kinda neat, especially if you like looking into the different connections involved in some conspiracy theories.
http://www.theyrule.net/2004/tr2.php and then pixel crack and physics combined!
http://www.falstad.com/ripple/ go check that shit out kiddies.