GOG Connect has updated, adding 17 titles for Steam owners to freely download. All you need to do is link GOG to your Steam account AND - if you own any of the games on the list - you'll get a free, DRM-free version of that game to download and keep forever.
If you like getting stuff for nothing, check out our list of the best free games.
If you do link your Steam account to GOG, be aware that this is a permanent tie, so it's no good if you're planning on using someone else's or getting a new account any time soon.
Obviously you won't have access to DLC or Steam Workshop with the GOG versions of these games, but you'll have the freedom to play them without booting Steam or anything else up.
The complete lineup of new titles is: AI War: Fleet Command, Anno 1404: Gold Edition, Baldur’s Gate: Enhanced Edition, Cossacks Anthology, Dex, Hit Tin Roof: The Cat That Wore a Fedora, Hotline Miami, The Last Federation, Olli Olli, Shadow Warrior, Teslagrad, The Incredible Adventures of Van Helsing: Final Cut, The Masterplan, Two Worlds Epic Edition, X: Gold, X Rebirth, and Ziggurat.
These titles won't be on the service forever, so take advantage now if you don't want to miss it. Just head over to GOG Connect and it's all pretty straightforward. There's also a back-to-school sale on over there, so you might grab a bargain while you're at it.