I know money is tight right now. It has been for a while and there's a chance it will be for a while.
I was researching where to advertise my newly free books and I realized that readers might appreciate a list of where they can find these books, as well.
Bookbub is number one. Competition to get a Bookbub Featured Deal (for authors) is fierce, and only 20% of applicants are accepted for their daily newsletter.
EReader News Today (ENT) is a good one with a huge audience.