The hackAIR project delivers a platform and apps for iOS and android on particulate matter pollution in Europe. It enables citizens to inform themselves on the risks, get involved in policy and planning, and to submit their own measurements from 4 types of sensors. See http://www.hackair.eu.
I worked on the SEO for my friend, a nutrition and health coach. The goal was to appear higher in Google search. I did some magic on her website, used the tools that Google so helpfully provides, and analysed the results. And voila, page 1 on Google and visible in Maps. The first customer came in through the website that same week.