If you need to start your week off with some new games, you should take a look at DRM-free store GOG.com as they have a pretty huge sale going on.
Before getting into that: they also have Serious Sam: The First Encounter free for 48 hours. No direct Linux support on that (they added it proper with the later Fusion engine release) but you can try your luck with the Wine compatibility layer. The other option is the Serious Engine itself, which is actually open source, so you could use the data files with it.
They also setup a few lists to look over including:
Some quick highlights of good games worthy of putting some time into:
- Shadow Tactics: Blades of the Shogun - 85% off
- Fell Seal: Arbiter's Mark - 66% off
- Tangledeep + Legend of Shara - 66% off
- Warhammer 40,000: Mechanicus - 50% off
- Tropico 6 - 40% off
- DUSK - 40% off
There's obviously a lot more, even just filtering for Linux supported titles on GOG there's over 400 discounted right now so you might find what you've been waiting on.
Head over to GOG.com for the full sale.