General public ebook/textbook resources
http://gen.lib.rus.ec (Use a proxy if you are having issues connecting)
http://www.alleng.ru/ russian site
http://www.eknigu.com/ russian site
http://www.freeetextbooks.com/ need to signup
http://forums.mvgroup.org (need to register)
Here’s a custom search engine for ebooks: http://www.google.com/cse/home?cx=000661023013169144559:a1-kkiboeco
Sites it indexes:
Academic Torrents (new site)
There are a lot more public torrent trackers, see here for more.
These last few are sort of specialized eBook private trackers, google them for some info.
You can also try googling phrases like ‘textbook/book title .torrent’ or ‘textbook/book title .pdf’ or ‘textbook/book title ebook’ or anything along those lines if you are getting desperate, but beware of malware, viruses, etc.
Private ebook trackers (Feel free to make a request for any of these in the Consolidated Invite Thread (see the no movement list in the OP)
http://myanonamouse.net (see reddit offers for invite)