I don't follow any blogs, but if I find some interesting post when searching for something, or having someone link it to me, I may read it if I find it interesting.
Here's an interesting one I came across the other day:
http://insidelisp.blogspot.com/
It's about someone exploring SBCL's internals, especially the compiler. A while ago, I did look at the frontend, so I was familiar with the things he talked in the first half of his posts, but I never did get far enough to be able to fully understand IR1 handler code, which is written in a pretty specialized compiler DSL. Funnily enough, non-portable x86 IR2 VOPs are actually understandable to me to some degree as I do know x86 asm.