College textbooks cost a disgusting amount of money. I didn't even buy half of my books when I was at school and I still spent hundreds of dollars per semester (and of course when you sell those books back you get about $2 total). If you have yet to live through this destruction of your bank account, brace yourself, and hope and pray for open sourcing.
Open textbooks allow students to have a digital copy of the required reading for free, or a printed copy for a price. Especially with the popularity of e-readers and tablets, this just makes sense. Also, lugging a million giant textbooks across campus is such a pain.
I love this graphic from Online Schools that explains the benefits of open source textbooks a lot more sensibly that I can, and is really good looking:
(graph via Edudemic / found via I Love Charts)