Minibloq is a programming language for Arduino motherboards designed to make it fun and easy for kids to make their own microprocessor projects.
How does it work? Well, it’s a bit convoluted but you basically plug in a board and program it using either graphical objects or text source code. It’s completely portable and runs on multiple platforms including the OLPC. The product will be technically free but the creator has built a Kickstarter page to help with expenses and he’ll send you an alpha version for a pledge of $39.
If you and your kids have always wanted to play with Arduino devices, this might be a great way to learn. Barring that, it looks quite cool.