When we were in WI @gretchengehrke, @mathew, and I were visiting some friends and we took a sample from a window at their house. The house window was facing a frack sand mine and appeared to be covered with a thin dust layer. We used a small razor and scraped the window in a downward fashion onto a slide. Since we just wanted to look at the materials that came off of the window under a microscope, we weren't worried about the sample size, contamination or anything like that. Made it pretty simple. I know @kgradow1 did something neat with tape on a rock recently as well.
Essentially tape, sticky pads have the advantage of capturing a record of actual particles that can be analyzed later. They can be scanned and digitized for standardized readings. More can be found on the Sustainable Aggregates website.