- Clockwise (supports ODPS! seems to be undergoing maintenance)http://xfmro77i3lixucja.onion/
- Imperial Library of Trantor (appears to be undergoing maintenance)http://c3jemx2ube5v5zpg.onion/
- Hidden book club (currently down)http://gen.lib.rus.ec/
- Library Genesis (Tor users may have issues downloading because of a per-IP download limit)
So I guess this list isn't that helpful at the time of posting, but yesterday and for the past year everything has been up so hopefully it will all be back soon.
If you haven't read the foundation series by Isaac Asimov yet drop everything and do that right now.
(rebooting this thread on the new and responsibly run Lainchan, this is really sleek guys.)