This site is broken down into the five main math standards and from there, it breaks it down into grades. These are excellent virtual manipulatives that students can use online. They are organized neatly and each one has directions on how to use them. Some of them are more confusing than others, but well worth it. My kids love using them.
This URL provides multiple math practices to be used by student in the classroom. The tacher can also use them as a way to show what is to be done on the board.
This website provides short videos of 'teachers-in-action'. My personal favorite is China through Mapping, as you follow an Early Childhood Teacher through the steps of a class-created GIANT map, all while learning about China. \nThe entire site is filled with great videos that 'teach teachers' about great classroom ideas!
K-12 resources in arts, foreign languages, literature, language arts, math, science, and social studies. These resources can be accessed for FREE at Learner.org or can be purchased through the website.
This site has excellent online activities, instructional aids, and games for younger elementary kids. I personally love the 2-digit with regrouping activities.