Take Control ebooks, from TidBits, is celebrating seven years of well-written, practical and easy to understand books about all things Macintosh, and a few other topics. You can read all about it here, but the gist is from now until the end of December, 2010 all Take Control books are 50% off. The special coupon link is here. These are books that are upgradeable, and are available in a variety of file formats, with topics like Take Control of Your Paperless Office and Take Control of Mail on the iPad, iPhone, and iPod Touch, Take Control of iPhone Basics and Take Control of iTunes 10: The FAQ. The entire catalog is here. I can personally recommend Take Control of Syncing Data in Snow Leopard, and Take Control of PDF Pen 5. You can see the table of contents for each book via links in the Take Control catalog, and there's usually a free sample of the book as well.
Take Control is the place I look first for a quick guide about anything Macintosh, and this sale is a perfect opportunity to pick up a few books for your friends and family (and yourself!) just in time for the holidays. It's a great addition to the iPod, iPad, or Mac you're giving as a present, and it's a lot of fun to buy a thumbdrive and load it up with books for that special Mac user on your holiday gift list.