home depot and lowes both have a fair good metal stock area. round bar flat stock, angle iron.
i helped my friend build landscape racks for all his equipment inside the new trailer he bought. all metal stock and hooks came from the depot.
http://i1097.photobucket.com/albums/...ps70caf8ab.jpg
http://i1097.photobucket.com/albums/...ps5416b144.jpg
we added maybe 6 more custom brackets/holders to it, and moved a few things around since these pics.