Random House maintains an archive of out of print books, which they will photocopy/scan for a price per page (I think it's 10p). About a year ago I was looking for a long out of print book (I found one copy for sale at around $250) and they were able to hook me up. They required I sign a form stating that the scanned book is for personal use only, and that I would not give it to anyone else. I suspect that I could have arranged a discounted group purchase if I thought other people wanted to read it as well.
The Random House archive is here: http://archive.randomhouse.co.uk/
I'm certain that other publishers have similar systems in place and would be very glad to take your money.