LensRentals.com is now accepting Canon EOS 5D Mark III rental reservations. Roger expects April 22nd to be the availability date and that meshes with the date I am hearing from others. Hit the Canon EOS 5D Mark III review placeholder page for preorder opportunities.
The Canon PowerShot G1 X is now available for rent. Though it will never replace my DSLRs, I'm really liking this camera.