eMarketer is the best single source for research and statistics on all manner of online marketing.  eMarketer employs a team of analysts that synthesize  data and primary research from over 4000 sources including consulting firms, government agencies and academics.

Their reports, data and interviews are easy to browse and search (probably because they employ Librarians!).   Content is organized by digital marketing channel (video, search engine, mobile, social media, email) and industry (financial, consumer, health care, entertainment) and searchable by keywords.   The digital world atlas provides country profiles of media penetration, usage, spending, and revenue with news and insight– essential references for any international marketing or management student.   Furthermore,  reports and charts are well documented with sources for data and insights clearly indicated.  Sadly many of the source documents they use are exceedingly expensive and not readily accessible in their entirety.

Tasked with ramping up the mobile strategy for a packaged food product?  Check out, Grocery Shoppers Hungary for Mobile Info.  Need to understand the online habits of  twenty somethings?  The indepth report Millennials Online:  Marketing to a Moving Target should be a good start.  Want to create appealing visuals for your pitch on using video to merchandize apparel?  Take advantage of eMarketers jpg tool to add charts such as this:

eMarketer is available on the Marketing Subject page and Databases A-Z.