Humble Bundle offers Steam downloads of the Humble Very Positive Bundle for Windows for whatever you want to pay. If you opt to pay the bare minimum of $1, you'll get Super Mega Baseball: Extra Innings, The Deadly Tower of Monsters, and They Bleed Pixels. That's $42 under the lowest price we could find for these games sold separately elsewhere.
If you pay more than the average, currently $6.25, you'll also get Hacknet, Crashlands, and UnderRail. Finally, pay $10 or more to receive Stephen's Sausage Roll and Curious Expedition. Your contribution can be donated to charity (St. Jude Children's Research Hospital and Special Effect), the developers, or both. Deal ends May 16.
Note: Many games are also available for Mac and/or Linux.