Great Virtual Manipulatives Site for PreK-8 Math

When it comes to virtual manipulatives, I have always been a big fan of the National Library of Virtual Manipulatives.  Today, I came across another great site that I plan to add to my resources!  This site is from Glencoe/McGraw-Hill.  It does not have quite as many manipulatives as NLVM, but the ones that it does have are very well done.   Here are a few of my favorite features:

-Geared Clock
-Balance scale
-Connecting Cubes
-A variety of backgrounds including game boards (with pieces), work mats, and story mats.
-Much, much more!