I've used the Plantower PMS7003 sensors for some DIY particulate sensors. I don't have a lab reference to calibrate against, but they should be pretty accurate as they are a laser sensor and the readings I got out of them were very sensible and consistent. Plus they include a tiny fan, which is important to get good readings. They are easy to use as well, it's just a simple UART digital interface. I also experimented with the cheaper Sharp IR dust sensors, but these were much less stable and also require constant calibration; they were ok for doing simple relative readings but they were clearly very inaccurate and unstable.

Sensing VOC's accurately is really difficult because most sensors have radically different (orders of magnitude) sensitivities to multiple compounds but can't actually distinguish between them. The readings typically get heavily skewed by the presence of minute amounts of some compound the sensor is very sensitive to. I tried several sensors and the best I could get out of them was a relative "good / bad" reading.