The obvious way of learning NSX is to go to a VMware class. But there are several other ways of learning the theory of NSX, to go deeper and in parallel with the practice you can do in the Hands on Labs from my previous blog post.
One of the best ways to learn NSX is to check and read about the VCP6-NV certification. Hopefully the link will work but if it gets outdated, google it. Three data sources I want to highlight that are available right now:
1) Read the blueprint in the exam link as this is what VMware thinks a certified professional should be comfortable with
2) Check blog posts from people who have prepared and studied for the certification. I particularly liked Richard Dowling's posts here https://richdowling.wordpress.com/vcp-nv/ and Fabian Lenz has a great collection of links here http://vlenzker.net/2015/11/lets-learn-vmware-nsx/
3) vBrownBag videos for VCP6-NV. You can find them here, in both english and spanish (I collaborated on a couple :) ) http://professionalvmware.com/?s=vcp-nv
I also want to highlight 3 resources that are in progress or will come soon
1) CloudCred is a game-type site focused on VMware and Cloud technologies. I highly recommend playing it, but in particular for the VCP6-NV exam, there are short tasks meant to teach you concepts. For a limited time, these tasks have bonus points as well:
2) Iwan Hoogendoorn, a CCIEx6 (!) has created vcix-nv.com, an awesome video tutorial site focused on the VCIX-NV certification. He has access to the installers, deployed it in his home lab, and is now creating and sharing a video for each VCIX-NV exam objective. Follow him in twitter and YouTube
3) The official VCP6-NV book will be released in Q1 2016. Below is my amazon affiliate link for it (means if you buy from this link, i get a very slight cut).