Invading from the Virtual Webber forums, I too have made several Arduino-based BBQ controllers. From the networking perspective I've found all the Arduino shields to be pretty disappointing so I ended up building my own "shield" consisting of a whole computer attached at all times.
Starting with my original Arduino+WiShield +DataFlash design:
To building the whole thing inside a Linksys router:
To finally shrinking it back down and bolting it to a Raspberry Pi:
The whole thing is open souce
too. I found this thread while googling around for similar systems for homebrewing but it is awesome to see some of the other great ideas in this thread!