With all the recent gloomy share price and economy outlooks, I guess it's nice to have some freebies :) Saw this freebie on Hacker News. 37signals' Getting Real (ISBN-13: 978-0578012810, $20.28 on Amazon) was first published in 2006 mainly describing 37signals' business principle. It can be useful for tech-startup wannabes or those in the industry. The HTML version was previously free, and they have just made the PDF eBook version free as well.
If you don't want to give up your email address to them, here's the direct link to PDF.
37signal's Basecamp product is fantastic for collab work. Will definitely take a read of the eBook, thanks Scotty.