To this, I will add that apparently hard anodized rims are structurally weaker than lightly anodized (the type that's usually used to dye Al) or non-anodized rims. So sayeth Lord Brandt:

http://www.sheldonbrown.com/brandt/anodized-rims.html

On an email (or was it netnews? whatever.) discussion, he mentioned that non-ano rims are harder and harder to come by. The Sun M13II was mentioned as a decent double-walled non-ano rim. I'm not sure if they're still in production, but when I got hit by a car a while back my bike shop had a machine built with an M13II for only $40 (cheapo Shimano HB-2200 hub). Just look for the shiny polished alloy rims, not the dull finish or black.

edit: I just did my homework. No, the question was about whether the M13II was ano or not. The poster claimed it wasn't because it was silver, but it seems like it's just a silver hard ano. Yes they're still in production. No you can't buy them, they're OEM only.
http://www.bicycle-forum.net/tech/Ne...ms_486154.html