Pattern Blocks are used in early math and just for fun. Great for drawing mandalas, tilings, and tesselations. Originally written as a toy for my daughter in 1998, this is my most popular app by a landslide. Latest version features full-browser resizing, better email, hundreds of backgrounds, and keystroke shortcuts. Now with Art Gallery for kid-safe sharing!
Mandalar is PatternBlocks for mobile! PatternBlocks is now released as a mobile app. See Mandalar. Still in Adobe Flex - all web/mobile platforms are cross-operable.