I just read the article on aluminum pens by James Mann but I can't find him in the members list. Does anyone know where I can get aluminum stock so I can give one of those pens a whirl?
I get mine locally as it is readily available. Most metal shops have it around. I like the 5/8" round stock to start. The 5/8" round is large enough for Barons, and Cigars. A larger kit like a Statesman would likely need a 3/4" stock. I would get half inch for smaller pens too. Enco sells it also like Kevin posted and they have great customer service. However, I get a 15 foot length for around 15 bucks. 6061 is what you want.
onlinemetals.com also has a wide variety of aluminum alloys, shapes and tubing, as well as a plenty of other metals. I've done business with them in the past and they seem reliable.
Call around to metal shops and get the prices. I bought an 18" round stock for about $30. I could have bought three 12' pieces for about the same price by buying bulk. But I did not want or need 35 extra feet laying about.