Ducksters
Ducksters: Kids Math: Multiplication Basics
Kids learn about the basics of multiplication including times tables, zero and one rules, and order on this site.
Arcademics
Arcademics: Canoe Puppies
Canoe Puppies is a multiplayer math game that allows students from anywhere in the world to race against each other while practicing adding two-digit numbers!
Other
Tufts University: Early Algebra, Early Arithmetic
This online resource is from the Tufts University offers lesson plans, worksheets, and ideas about using algebra with elementary grade levels.