I have these shelves from Target:
http://www.target.com/Madison-Loop-L...ntique%20White
They also come in black and walnut. They are very sturdy. I even took out the second-to-bottom shelf in order to be able to put the 12x12 Cropper Hopper Paper holders on the bottom shelf and they're still sturdy. They're easy to put together too, I did it myself pretty quickly.
I have 2 of these shelves, then the desk that is in the same style (which is also quite sturdy - Hubby even sat on it!), but I bought it in black, and i have the white chair. The one thing I'll warn you about is that these are all "distressed"/"antiqued" as in the paint is not on evenly - it has streaks pulled off. Personally, I love the look but I did read a lot of mad peoples comments who did not expect it, so I thought I'd throw it out there.
The other thing is these are not available in the store. I just waited until it had free shipping and was 15% off (like they are now) and bought them. I love them and would totally buy them again!
Hope that helps!