Where to get decent building materials???

Hopefully this thread will expand to cover a broader range, but here is what I am looking for:

If you go up the stairs in my house, there is a hallway to the right. The first 66 inches of the hallway is 8" wider than the rest (i.e.: there is an 8" x 66" space on the right side that is perfect for some kind of shelving).

I have wanted to make some really cool shelves (approx 1" thick, with custom cast spacers to hold them up). The shelves would be radiused at wall adjoining the stairs.

What I really would like is black annodized aluminum, but would consider other materials.

My question: Where the heck can you source anything like this at a reasonable price?? I've seen some artwork that used aluminum like this, but most metal dealers don't seem to have anything near the dimensions I want.

Any ideas??

p.s.: If anyone knows a good source of rosewood in say 1x4 or 1x6, I have someone who sorely needs that too!