I tested almost all of the backs on the market last year, and have extensive reviews here of several 16MP backs, including the now discontinued Kodak DCS Pro Back, Leaf, and Imacon, and as well the current Phase One P25 22MP back.
There are several new 22MP backs now coming on the scene, and I expect to review them as samples become available.
To my knowledge there is no other site on the Net that reviews such backs on a regular basis.
Michael