I have found a business to match that of Hubspot’s free resources: IIG Insights Interactive Group (www.interactiveinsightsgroup.com). Run by Robin Broitman (http://twitter.com/rgbroitman) and Jon Eastmond, IIG has thirteen free resources (a combination of guides and lists) including a guide to linkedin, twitter, delicious bookmarking, building brand identity with social media, and a superlist of social media metrics resources. As an example, the social media metrics superlist links to fifteen (15!)published studies from 2008. An absolute gold mine for further research.