Where can I get some paper/doc/whatever which describes how a Haskell compiler actually works? I read quite a few of the docs of GHC, but stopped after getting a headache. So, something which doesn't require a PhD to understand it and isn't written in the You're-supposed-to-be-already-familiar-with-it style would be preferable. It's not a problem if it's really long and takes some time to understand it though.
PS: Most interesting would be something about GHC, but anything is ok.
You can get an answer from the horse's mouth! Simon Peyton Jones (GHC wizard) wrote a book explaining how to implement functional programming languages. It's available for free online since it's now out of print: http://research.microsoft.com/en-us/um/people/simonpj/papers/pj-lester-book/
Of course, GHC has moved on since the book was written, but it's still very relevant.