I don't think there is one good resource about learning SIMD optimization.
Intel optimization manual is good, it touches are lot of details, but I think they assume you know some kind of SIMD programming. Anyways - it is a good resource.
There is also similar manuals from AMD:
http://developer.amd.com/resources/developer-guides-manuals/
I recommend reading Agner's optimizations manuals:
http://www.agner.org/optimize/ They have a lot of interesting details and they touch SIMD optimization in few places.
Additionally you can search for some presentations from game engine developers, they often have nice presentations about SIMD. For example:
SIMD at Insomniac Games
Culling The Battlefield
Physics Optimization Strategies
Try searching for the titles of presentations on Youtube or GDC site, they often have presentations recorded.
Fabian Giesen articles on optimizing Intel Software Occlusion Culling are nice:
https://fgiesen.wordpress.com/201...izing-sw-occlusion-culling-index/ (and check out other SIMD blog psots on his site)