Compiler/OS Design - Where to start [closed]

Question

I have a fairly strong background in C and Assembly and I am starting to look into basic compiler and operating systems design, but my biggest problem is where I should really start, seeing as both are very large project types to undertake.

My question is, what are some good resources or good known starting points when looking at getting into either of these programming arenas?

ADDENDUM

As I've been reading along over the past few months I've found that basic principle and theory are roughly similar, it's more of a I want to get into lower level design and want to know where to start, since much of what I've been reading has been theory and I haven't ran across a large amount of practical implementation information.