That kind of shelving (not really a rack) is ubuiquitous, and with good reason: sturdy, easy to put together. If you peek into a restaurnt kitchen, you'll probably see some sheving like this. The cool thing is that it uses its own weight to keep the shelves in place.
This shelving is sold by most big-box stores under a variety of names. They're easy to spot because the posts have a lot of horizontal grooves that catch the sleeves that hold the shelves up.
If you want a specific source, there's Metro Commercial. Their consumer line is mainly sold through Container Store.