Interesting read:

 - http://built-envi.com/portfolio/ultrafine-particle-emissions-from-3d-printers/

It looks like activated carbon filters would be a strong performer for ABS (styrene) and PLA (lactide):

 - http://www.sentryair.com/activated-carbon-filter.htm

**Are there better filtering materials or processes than filtering the air through activated carbon filters?**

Here's an example filter setup:

 - This fan mount: http://www.thingiverse.com/thing:780001
 - 60mm fans and this filter: http://www.amazon.com/gp/product/B00XNI5SY4/ref=s9_simh_gw_g201_i5_r
 - And sandwich the filter on the fan using this fan grill: http://www.thingiverse.com/thing:11906