It's easy to forget that there are other PC game services beyond Steam. GOG (formerly Good Old Games) has made a name for itself selling older software, but now it's stepping up to the major leagues with a DRM-free alternative to Steam's software, called GOG Galaxy.
The new service is currently in an open beta available on Windows and Mac. GOG Galaxy allows you to manage and update your game library, much like you do on Steam. It also includes a community layer, so you can track achievements, and play and talk with your friends.
There are a few key things that make it stand out from Steam though. For starters, you can play your games offline, no strings attached. While technically this is possible on Steam, it requires you to enter Offline mode before doing so, which can be problematic if you lose your internet connection. You can also download backup copies of your games to your PC so you can install them even if you lose access to your GOG account.
To sign up for the beta, hit the source link below. You'll need to create or login to your GOG account and then click the "Join GOG Galaxy Beta" button.