Nils M. Holm's t3x.org is filled with the most wonderful toys. An example:

"SubC is a fast and simple public domain compiler for a clean subset of the C programming language. It can compile itself and passes gcc -Wall -pedantic. Its internals are described in detail in the book Practical Compiler Construction. Note that SubC is a teaching vehicle rather than a production compiler."

https://t3x.org/subc/index.html

And when I say toys, I don't mean mean plastic, trivial items. I mean, I want to buy all of his books, download all of his tools, and collect the whole set, like Legos or other toys never did for me when I was a child.