Amazon is once again holding a sale on downloadable titles for the PC, offering some truly killer deals on games including some popular co-op titles. The Serious Sam series seems to be the centerpiece with Serious Sam HD: The First Encounter, Serious Sam HD: The Second Encounter, and Serious Sam 3: BFE all available for 75% off. Co-Op friendly 4 packs of the HD remakes are available for $10 and $15 for the first and second respectively, while SS3 is available in a 4 pack for $30.
You can find the full list of games available over at Amazon.
Source: Amazon.com