I'm currently using a Netduino, and damn they are nice. The forums at http://www.Netduino.com are very helpful as well. I have communication over I2C in a matter of minutes, controlling my valves. I've also figured out how to wire up LCDs.
There is someone else in the forums discussing PWM and heater control. I'm assuming they are also automating their brewing. I'm currently stuck trying to integrate WiFi with the damn board though. Then my automation POC will be mostly complete. Then it will just require me building up the logic from the simple pieces to control flows, temp, etc.
My goal is to have the control panel wired up this weekend, so next weekend I can go through the first wet test. (Assuming the electrician comes next week to install my 60A service)
OK stupid question time but what exactly goes on the netduino when you compile for one? It doesn't exactly seem to have a lot of extra space to put even a micro .NET framework.