Tim Dye provided the following docs that summarize work he's been doing in this area over the past few years.

"report from a project we did for the US EPA to characterize the quality of low cost sensor technologies. We worked with 2 groups and the results are promising, but more work is really needed to make the low cost sensors sensitive to ambient pollutant concentrations.
I created table to summarize the range of pollutants and what’s needed in terms of accuracy and other characteristics for low cost sensors. **NOTE: Units need to be corrected-- EPA's PM standards are in micrograms not milligrams per cubic meter, so it should read 35 ug/m^3 as the 24 hour avg. standard, for example, not mg/m3.
A list of commercial AQ instruments that range from low-cost to mid-cost. discusses how to read radon gas in the home looks at Dylos DC1100 Pro Air laser particle counter and the Sharp Dust Sensor looks at the Grove /Shinyei Model PPD42NS Dust Sensor discusses how to use Dylos DC1100 Pro Air laser particle counter with an Arduino to post data to COSM/Pachube looks at the Sharp GP2Y1010AU0F Dust Sensor
Experiments/Comparison study with Sharp Dust Sensor:

Sensor Datasheets

Application Notes / Guides

- Characterization information from the manufacturer of the sensors Tutorial about the low cost DHT temperature & humidity sensors.