Eli Bendersky's website Pure delight !!!
Have you ever tried debugging a program written in machine/byte code (the level *below* assembly) ? Maybe you did. But was it machine code of a virtual machine written by you, and was it a debugger written by you ? Now, maybe you haven't had the opportunity. Try it ! It's fabulous !
I'm back to some MIX development. Now I'm improving my virtual machine implementation to be more robust - testing it on some of Knuth's programs from the book. The first program I typed in didn't work - que pasa ?? Fire up a debugger... err... what debugger ? Oh, no problem, lets write a simple debugger. It turned out to be trivial (the debugger is something like gdb, text oriented one letter commands). It's not full functionality yet, but it's evolving (I add stuff to it on a "need-to" basis).