I’ve Twittered and Facebooked the air quality indicator (AQI) measure a few times, but I don't think the numbers mean much without visuals. So, every so often, I'll post a photo from my office with the AQI score. I'm getting my data from the US Embassy's Twitter feed. (Note, the US Embassy is on the other side of Beijing from my office, but I trust the data more than the official Chinese gov't info.)
Here's what 213 looks like. (Average for the day is 199). The AQI in Bellevue, WA is 24 currently.