[dchapp]

I see several people sharing the Stanford bithacks link, so I'll throw in a slightly-less well-known resource that I found particularly instructive. Basically, a collection of the lemmata we can prove about fixed-length sequences of bits and the fun algorithms that can be built atop those results.

https://www.jjj.de/fxt/

And for the non-pdf-phobic: https://www.jjj.de/fxt/fxtbook.pdf