Not all blogs have to sell ad-space to gather revenue, some sell their skills. Like the PSFK blog posse, who have started to produce a range of products and services based on their trend spotting skills. If you haven't heard of them yet, PSFK is a collaborative trend spotting blog that is read by marketers around the globe.
Clients such as Anheuser Busch have commissioned the PSFK team for their services which includes trend reports and managing client's very own trend blogs. You can see more over at check services from PSFK.