those planters specifically are from, but Inner Gardens has a few great planters that are the same modern style, and a similar color.
Here's one to give you an idea: http://www.houzz.com/photos/169937/Inner-Gardens-Fiber-Cement-Arrow-Planter--outdoor-planters-
Design Within Reach is another great resource
Not sure where the planters are from but a good place to get similar planters is : Inner Gardens -one planter from Inner Gardens
cement block planters.....so simple yet hip and cool looking
planter design as a focal point
spill from planters lining a walkway. The variety of plants used in each one adds interest, though using a single plant would work just as well.