I demo the idea of canceling units out with dominos using the smart notebook and then have the students work in groups using the cards to simulate dimensional analysis and answer the questions on the worksheet. I like having them find two different ways to solve each problem; this helps students learn that there is often more than one path to take to find an answer.
There are 8 full sets of cards, so that you can keep class groups fairly small. Each file is named by the font color. I use different colors to help groups keep their cards separate. When printing these cards, I used Avery business cards so that I would have minimal cutting. Each business card only needs cut in half. Cards should be printed front and back (page 1 and 3 go together and page 2 and 4 go together).