Great idea! I'll put one together in a couple days on Github :)

There is a directory of sorts here: https://github.com/nayafia/microgrants

(Not with deadlines though, as far as I am aware.)

Yeah I came across that, it doesn't really seem actively updated + some of the microgrants that are listed there are inactive now

I "watch" it on Github and it still gets updated. If notice out-of-date things you should open an issue or a pull-request.