I have a mesh network of atmel 328p using nrf24l chips. The connection isn't super fast but the chips are cheap (~$1 ea. at 10 on a board ready to go), and I do

I have a mesh network of atmel 328p using nrf24l chips. The connection isn't super fast but the chips are cheap (~$1 ea. at 10 on a board ready to go), and I doubt there's anything I could/would do with a 328p that would max the data rate. They'd probably work pretty well for a low speed link on the pis. Only caveat I've found is that they're extremely picky about getting clean power on the +3.3V rail.