I agree strongly with you about the need for good resources. Here are a few I've found that are useful.
* A trip through the Graphics Pipeline[1] is slightly dated (10 years old) but still very relevant.
* If you're interested in compute shaders specifically, I've put together "compute shader 101"[2].
* Alyssa Rosenzweig's posts[3] on reverse engineering GPUs casts a lot of light on how they work at a low level. It helps to have a big-picture understanding first.
I think there is demand for a good book on this topic.
[1]: https://fgiesen.wordpress.com/2011/07/09/a-trip-through-the-...