Gizmos are great applets for exploring math and science concepts. 

Virtual Science experiences. 

Freefall on Mars applet from University of NewFoundland

Free falling body applet that gives you the option of dropping from a height or firing upwards from the ground. 

Applets are small, self-contained, interactive programs that can be run on your computer using code called Java (a free download from Sun Microsystems). All of the applets listed below are available for download from the web, but require Java to run. An Applet Search Engine can be used to find other available applets not found on this page.

Welcome to the Physlets resource page. Physlets, Physics Applets, are small flexible Java applets designed for science education.  You do not need to become a Java expert in order to use Physlets.  The links on the right contain tutorials, download instructions, and example problems to help you use Physlets in your teaching.

Fowler's Physics Applets. Michael Fowler - University of Virginia Physics

PHYSLETS were developed at Davidson University by Wolfgang Christian. They are java applets that can be called from some javascript code in a web page. The links below contain physlets written or adapted for use at LTU, Lawrence Technical Univ., by Dr. Scott Schneider

Math applets from Edinformatics. 

More physics applets from Edinformatics. I don't know exactly who they are but they have their applets organized by content/level/topic which is a great way of helping people find applicable apps 

More physics applets 

Projectile motion applet. Easy to manipulate and set inputs. 

Physics applets from university of oregon. department of physics. 

Keep this article close by, so when you need it, it will be available. I wouldn't be able to memorize all of the information, but when I am working on or in anyone of these products the cheat sheet would be a valuable resource for expanding my shortcut repertoire!

As I read this blog, I immediately thought of the article Never Say Anything a Kid Can Say. It is a very similar set of lessons for students and teachers.  If a student can say it, then why am I? B/C I am the expert... but who is learning in that situation? Me of course b/c I am the expert!!  Also, if a kid says it, it builds their confidence/understanding and allows the teacher to probe to help the student develop their analytical skills rather than their passivity and incompetence skills.  This blog is worth a very long read and analysis. I also, think everyone should look for the article mentioned above and see if they couldn't learn a few things by saying less!

Nice set of applets that let students explore fraction understanding from multiple perspectives and models. I love that they use a variety of models for fractional development, including bars (multiple versions), sets, and linear. From the site:  "Why Fractions? Fractions are one of the earliest stumbling blocks for students in math. Our goal is building conceptual understanding in fractions as a basis for comprehension in all later topics."