I bought and installed a http://www.amazon.com/CF10285-Fresh-Breeze-Cabin-Filter/dp/B001CEG90I/
Nothing wrong with the existing filter, I'm just in maintenance parts acquisition mode.
The cabin filter is a piece of cake to remove. See 2012 Toyota Camry SE: What's In There?
for pictures and instructions on removing the filter.
You can vacuum, blow, and tap out the dirt from your current filter if you're not ready to replace it yet.
There's also a $3 Fram Cabin Filter Rebate ending August 31, 2012 with a limit of 2 per address.
It fits perfectly. The Fram instructions say to install it with the air flow arrow pointing down, but the 2012 Camry air flow direction is up, so I installed it with the arrow (darker, carbon treated side) facing up.
One insignificant difference I noticed is that the stock filter has 15 pleats, the Fram has 14 pleats.
The Fram filter is has a mix of active carbon and baking soda woven into the fibers of the filter. I'm not sure if the stock filter has active carbon or not.
I have not noticed any difference with this filter installed vs the stock filter, but I've only driven 20 miles or so with it and did not encounter any stinky air or vehicles in front to test it with.
When you pull out the currently installed cabin filter, look at the bottom, because that's the dirty side. I'm not sure why Toyota designed it so the dirty side is down, because this means some dirt falls down out of the filter and cannot be cleaned without disassembling the HVAC system. I wonder where the dirt that does not get blow and caught by the filter ends up and how to clean it out
I hope this helps someone and you are
***** 09/01/2012 CORRECTION TO DIRECTION OF AIR FLOW STATED ABOVE: *****
The air flow direction is top to bottom, as evidenced by holding a piece of paper in the air filter slot and turning the fan on. Therefore the filter should be installed with the air flow arrow pointing down, which also results in the darker charcoal covered facing down.