Well, I download every free book that
looks interesting.
Correction. I haven't downloaded most of the Mobileread library or Gutenberg library because the vast majority of those are A) not interesting to me, B) I know they will be available later. I also do not scour feedbooks and other places, but if I happen to have a link to an interesting looking freebie under my mouse cursor, I download it.
I grew up on Library books, and you quickly learn to be a opportunist when you are a fast reader and you rely on a small handful of relatively modest libraries - the town library, the county library, several school libraries, ...
I have discovered lots and LOTS of books and authors I would not have found otherwise. I also do not hesitate to leave the book unfinished if it turns out to be boring, or wrong genere, or I simply decide that I do not like it.
I have quickly found out that there are some offerings that are available only for a short period time so when I see a contemporary book that might look interesting, I can always find another few megabytes of free space on my disk. I can always delete the book if it turns out it is not that interesting, but sometimes when you read a good review for a book that was available for free and you return to download it it is not available anymore.
At one moment I was even doing critiques at
www.critters.org - you get to read a story or a book and in return you write a meaningful critique. The books are very, very new, done by beginning authors that need somebody to read the story or a book and provide feedback.