- Count Us In
A site full of downloadable activities and games for early number development.
The Eisenhower National Clearinghouse site providing links to activities and lessons on number concepts such as counting.
- Let's Count to Twenty
A series of seven lessons designed to develop students' number understanding up to 20. Blackline Masters are included. One of several early number lessons on the Investigations website.
- Number sense development
This link leads to a research article focusing on young children's development with number sense. The article is published by international authors but still cites the National Council of Teachers of Mathematics' Standards regarding number sense development.
- Q & A on number concepts
This is a part of the Math Forum website that lists interesting questions and answers on many number concepts.
- Ten Frame
A nice manipulative version of the ten-frame (applet). Probably best used by the teacher because the text is quite small. Students use counters and enter a number that answers a question. There is also a five-frame applet.
- "Zero to Three" Program
This site is part of the Center for Program Excellence's "Zero to Three" program. The site gives research supporting the importance of developing number sense in very young children, as well as giving suggestions to parents for doing so.