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With the clamping diodes I don't see much of need for the op-amp. I guess you get the drop from 5V to 3V, however you can do that with a resistor divider. I don't see much of a need for R9 or C5. Perhaps that op-amp is sensitive to RF noise on the front end. C1 - C4 are not ESD protected, they could be damaged.

R5 - C5 are a nice RC input filter, takes out a lot of hash.
Ditch the opamp and clamp diodes, use a resistor divider and a transorb. I used these http://www.semtech.com/images/datasheet/srda3.3-4.pdf for my i/o protection.

Another option without using an operational amplifier. Various configurations of the resistors can be used for different sensors.

Remember your 5V has to be push / pull, as over voltage will dump current into the 5V rail. If you don't drain that energy, the 5V will rise. I think I see you use a lightly loaded zener else where, to keep it pulled down. Also you have to make sure the diodes are low leakage, 10uA of leakage would generate .1V.

Yet another idea. We can raise the power supply voltage of the op amp and provide a full range of the output voltage. Op amp has a good power supply rejection ratio. LC-filter provides an additional suppression of the high frequency components of the supply voltage.

Hmmmm, sounds like this would be more ratio metric as well. Well ratiometric if you have a 12V sensor.