Someone posted this article on Facebook, I found it interesting and liked how it focuses on stabilising the core rather than crunches. Although some of the claims seem a bit far fetched.
Would appreciate more experienced people's thoughts on the article
http://robertsontrainingsystems.com/blog/understanding-your-abs-part-ii/ 
Mike Robertson is a very smart guy... though I wish he wasnt so damn wordy with everything. That was painful to wade through.
I completely agree that stabalization should be a big focus when it comes to core training. The ability for the abs to resist movement is just as important as their ability to apply force. Crunches are pretty much a waste of time if you are doing things like front squats, heavy carries and sprinting(which you should be doing).
Ab wheel roll outs and hang pikes have been very good to me
I've been doing a pilates class for a few weeks now and adding more TRX training. My back certainly feels better and I feels better body structure when I'm practicing.