Today in arxiv has appeared something that I had never seen before, a whole collection of review articles devoted to a single topic, the ADS/CFT. There is an "overview" article that serves as reference of the others: Review of AdS/CFT Integrability: An Overview.
If I haven't counted bad there are 23 articles. And this is a review!. Clearly that is an indication of the fact that AdS/CfT is a very active line of research with many branches.