Kevin,

I have also, used Metal Supermarkets for some stuff, especially the drops section.
They have some unusual sizes at times, but for small quantities they are great.
I picked up some 1 1/4 X 1 1/4 X 14" for some hardie posts last year.

The site I use the most is Atlanta Steel Mart - 770-416-6999, Atlanta Steel Mart
They will cut small quantities, since my truck has a short bed.
They also carry some ornamental pieces ready to weld in, Post tops, balusters and the like.
They are off Buford Highway at 2805 Amwiler Road, across from Newell recycling.