Here's a good page about bike parking. If you scroll to the bottom, there are links to manufacturers, as well as other references. In my opinion, there are three overarching guidelines:

(1) The rack should support the frame of the bike, not the wheel. It should be simple to pass a U-lock through the rack, the frame, and one wheel. There are plenty of designs out there that will accomplish this. Unfortunately, where I live the wheelbender is king (where racks exist at all).

(2) The rack should be securely mounted in the ground. Ideally, it should be embedded in concrete, but at a minimum it should be secured to concrete with tamper-proof fasteners.

(3) Simply providing a rack is not sufficient; consider siting and orientation. Bikes should not be crowded, and it should be easy to move the bike in and out of the rack, even when racks are full. If it's a rack like the Cora that allows access from both sides, make sure it's accessible from both sides by placing it perpendicular to walls or other barriers.

Wrong:



Right: