Steam offers downloads of Portal 2 for Windows, Mac, or Linux for $4.99. That's the lowest price we could find by $11, although we saw it for a buck less last month.

Steam also offers downloads of the Portal Bundle for Windows, Mac, or Linux for $6.24. That's the lowest price we could find by $14. It includes Portal 1 and 2. Both deals end January 30 at 1 pm ET.