Hg (http://mercury.sexy/hg_sdf/) is a great resource. I'm not a fan of the non-commercial license. The intro on the top of the site has a lot of great links to resources outside of iq, including the pouet.net thread on Raymarching, John Hart's original sphere tracing paper, and enhanced sphere tracing, as well as the author's original talk from NVScene 2015 (https://www.youtube.com/watch?v=s8nFqwOho-s). Definitely check out all of these resources.
Voxel Quest (http://www.voxelquest.com/), a "failed" kickstarter project, has some good write ups of how he's built the engine over the years as well as source code.
There are of course more resources than that, and just browsing shader toy and reading people's shaders can give you a ton of knowledge, but that's the short list of resources that I've found enlightening over the years.
If you're more interested in signed distance fields outside of the shadertoy\demo scene use cases there are a lot of interesting resources out there written by people using them in more complex contexts. Alex Evans (Media Molecule) Dreams talk is awesome. You can see the talk here (https://www.youtube.com/watch?v=u9KNtnCZDMI) and read the slides here (http://advances.realtimerendering.com/s2015/AlexEvans_SIGGRA...).
https://www.gdcvault.com/play/1015455/Advanced-Procedural-Re... covers how to generate meshes. With modern hardware with ballot\shuffle there are probably more efficient ways to do this in a compute shader now, but the talk is still good.
Epic games siggraph presentation (http://advances.realtimerendering.com/s2015/DynamicOcclusion...) is a good explanation of how UE4 uses signed distance fields for ambient occlusion and shadows.
Q-Games presentation (http://fumufumu.q-games.com/archives/TheTechnologyOfTomorrow...) on how the now defunct Game Tomorrow Children uses signed distance fields for dynamic world space reflections.
Voxel Quest (http://www.voxelquest.com/), a "failed" kickstarter project, has some good write ups of how he's built the engine over the years as well as source code.
Unbound.io gave a talk at GTC 2017 (http://on-demand.gputechconf.com/gtc/2017/presentation/s7777...) that goes into some detail on their signed distance field VR sculpting app.
There are of course more resources than that, and just browsing shader toy and reading people's shaders can give you a ton of knowledge, but that's the short list of resources that I've found enlightening over the years.