Neat stuff:

Named Things in Chemistry & Physics (and genealogies) from YorkU

Historical Timelines for Science & Math Developments: http://history.hyperjeff.net/

Get a feel for orders of magnitude, from galaxies to protons: Powers of 10

How do common things (like microwave ovens, etc) work?:  How Stuff Works

And another source for what's under the hood:  How Things Work

What's this stuff? How common things are made.  http://pubs.acs.org/cen/whatstuff/stuff.html