Amazon offers its Prime members Dark Souls for PlayStation 3 or Xbox 360 (pictured) for $12.99 with free shipping. (Non-members can spend $25 or more to qualify for free shipping; otherwise, shipping costs $4.98.) That's $2 under our Cyber Monday mention and the lowest total price we've seen for either version. (It's a current low for both platforms by $7.) Sales tax is added where applicable.
Orders placed by December 21 at 7 pm ET using Prime (or December 19 at 3 pm ET using Super Saver Shipping) are guaranteed to arrive by Christmas.
Update: Best Buy charges the same for PS3 and Xbox 360. (Free shipping is available for all customers.) Order by December 19 at 1 pm ET for Christmas delivery.