Definitely for today, Double Fine will get a lot of attention, because, aside from releasing the Linux port of the remastered version of Day of the Tentacle, they're offering a 52% discount for the whole Double Fine Bundle on Steam.
The Every Game from Choice of Games bundle is currently with a 25% discount because of the Steam Summer Sale. It includes 30 stories and a couple of DLCs for some of them.
OpenMW is the open source game engine for Morrowind that is really quite amazing. If you've been wanting to try it out but you don't own Morrowind, now is a good time. GOG has it on sale for cheap.
If you're in the market to pick up something for the weekend, be sure not to miss out on the excellent XCOM 2. It's currently 33% off for the weekend on Steam, cracking deal that is!
The current Humble Weekly Bundle: Orbyt Play offers six games of which are three for Linux and one that is partly supported by now. Only one of them is DRM-free, the others are Steam-only.