I really want to communicate wirelessly between Arduinos for cheap. I love the idea of “The Internet of Things”, with everything I can look, see, touch all connected together. The problem is the cost. Zigbee modules seem to be the standard, but they are just too much to be a reasonable solution for putting everything on the Internet.
The Nordic nRF24L01, built into a small module and sold by mdfly.com for $6.50 is an excellent solution. It’s cheap, fast (2 Mbps), easy, reliable, and low-power. It entirely implements the Data Link Layer in hardware, handling addressing, collisions, and retry, saving us lots of work on the software side. Zigbee has the brand recognition, but this little guy puts it to shame.