Since the original post was from Long Island, I suggest you use:
Yarde Metal
999 Motor Parkway Hauppauge NY 11788
Phone: 800.333.2024
Fax: 631.232.3200
I am in NJ and they have a location within a half hour of us that we use all the time.
First, there is a delivery minimum most likely, however, if you own a pick up truck you can just make the drive and get your order. It takes one - three days depending upon where the particular item you want is located. The 6063 C channel we wanted was in the CT location, took 2 business days.
Realize that you will likely be picking up metal in 16 to 20 ft lengths. Bring a hacksaw with you and just cut it in half or for our purposes we needed it in 6 ft ish lengths so we cut the first 6 feet off and the 10 ft fit fine in the truck.
Their sales people are wonderful and they can find almost anything for you. I have used them for 10 years. They do not, however, have an online catalog, which is annoying, but they emailed me the 2 pages of 6063 channel options so I could tell them exactly what I needed.
I am not sure who mentioned delivery into NYC, but I don't see why Yarde won't deliver to you. They have locations all throughout NY, NJ, CT.
http://www.yarde.com/