I've had a German smoked beer that was really good. It was brewed in Bamberg, Germany, which apparently is where the tradition started. They smoke the malt that is used in the brewing. Not sure what kind of wood they used.
I have heard of the Alaskan Smoked Porter. Funny story, their brewery is located across street from a salmon smoke house in Juneau and the owner of the brewery asked the salmon guys to smoke his malt for him. They used Alder, for the obvious reason that it's what they used in the salmon.
I think Rogue also makes a smoked porter and if I'm not mistaken, Brooklyn Brewery also makes some type of smoked beer as one of its seasonals. I also saw a beer once called "Smoke on the Porter", but not sure who brewed it, though it was an American craft brewer.
I don't think it matters what kind of wood you use, just give it a nice smokey flavor. Good luck and be sure to let us know how it turns out!