Two Neat Sites, and a Question

I just came across links to these two educational websites.

This one helps you comprehend the size of an atom.  Quite fascinating!
Cell Size and Scale

And this one has a short educational video for each element on the periodic table.
The Periodic Table of Videos

These are both interesting and useful websites that I would like to use as supplements when it comes time to study biology and chemistry with my children.  But there are many, many interesting educational websites like these that I would like to use in the future.  I'm not really sure how to keep track of them all!

So here's a question for other homeschooling parents.  How do you keep track of educational websites that you would like to use in the future?  There are so many fantastic resources online, how do you organize them all?  Any thoughts about the internet as an educational resource would be appreciated. :)