We have used these blocks for so many things. I bought them 12 years ago and they are still getting alot of use:
Most recently, we have been using them to do the Stamp Game that is in the Montessori Curriculum. The regular stamps have the actual numbers on them 1, 10, 100, 1000, however I thought it was the color that truly matters. I have been using Montessori For Learning Stamp Cards and I also use the Stamps with Z Man's Singapore Math 2.