National Council of Teachers of Mathematics
The Math Forum: Famous Problems in the History of Mathematics
On this site, there are several math problems to explore and solve. Look through some solutions by famous mathematicians and expand your thinking about some interesting math concepts. Teachers of elementary grades may want to use this...
CK-12 Foundation
Ck 12: Earth Science: Evolution, Plate Tectonics, and Climate Change Study Guide
[Free Registration/Login may be required to access all resource tools.] Summarizes the key points about three theories in Earth Science: the theory of evolution, the theory of plate tectonics, and the theory of climate change due to...