educational software

I want to teach any of the younger grades of kindergarten to third grade. One of the 3rd grade standards is understanding the relationship between the force applied to an object and the resulting motion of the object. I really liked exploring on phunland.com. I feel that with some help and assistance, the students would be able to explore this property on this program. i feel that this program's content is very appropriate, but it is not as easy to use. This program is not one that is very easy to figure out right off, it is not self explanatory. Although it is not easy to use at first, with help I feel the students could explore this program.
The mars quest link was also very interesting. I liked how the pictures were very realistic, and gave you a good opportunity to explore. It was fun and easy to use. This program would be helpful in teaching the 3rd grade science standard 1 of understanding the shape of Earth and the moon are spherical and how they rotate.