I have several of these Ikea floating shelves I got at an estate sale. The instructions claim a pretty low weight capacity rating, I think around 20 pounds. I attached them to studs instead of using anchors, so maybe they can hold more that way. I think one has more than 20 pounds of Trimline phones on it.
You can buy brackets to make your own, these claim they can support 50 pounds, but with an 8" deep shelf, too shallow to support TVs.
http://www.rockler.com/blind-shelf-supports