Decimal Squares is a program for teaching place values and the use of decimals. Decimal Squares was developed by Professor Albert Bennett at the University of New Hampshire. The bulk of the program is a series of classroom materials and books that are available for purchase. One aspect of the Decimal Squares program that you can access for free is the games section.

The games section of Decimal Squares offers eight interactive games that students can use to develop their understanding of place values.

Here are some related resources that may be of interest to you:
The Sliding Block Puzzle Page
A Great Collection of K-8 Math Resources
Kids Numbers – Learning Math Step by Step