Yahoo! Social Bar takes the No. 1 spot on our list of top non-game Facebook apps growing by monthly active users this week, adding 1.2 million MAU.

Titles on our list gained the most MAU of any non-game apps on the platform, growing from between 300,000 and 1.2 million MAU, based on our AppData tracking service.

Top Gainers This Week

Name MAU Gain Gain % 1.  Yahoo! Social Bar 36,700,000 +1,200,000  + 3% 2.  Instagram 25,800,000 +1,000,000  + 4% 3.  YouTube 2,700,000 +900,000  + 50% 4.  Washington Post Social Reader 3,800,000 +800,000  + 27% 5.  Spotify 26,500,000 +700,000  + 3% 6.  Zoosk 13,100,000 +700,000  + 6% 7.  HTML Page Tab #8 3,300,000 +400,000  + 14% 8.  Birthday Reminder 2,400,000 +400,000  + 20% 9.  Photo Love 9,500,000 +400,000  + 4% 10.  Silp 440,000 +350,000  + 389% 11.  HTML Page Tab #10 3,200,000 +300,000  + 10% 12.  Static HTML Iframe Tab 3,800,000 +300,000  + 9% 13.  HTC Sense 5,900,000 +300,000  + 5% 14.  Mynet 2,200,000 +300,000  + 16% 15.  BranchOut 2,000,000 +300,000  + 18% 16.  Ask.fm 2,700,000 +300,000  + 13% 17.  The Fan Machine 1,500,000 +300,000  + 25% 18.  Voxer 2,600,000 +300,000  + 13% 19.  Samsung Mobile 19,500,000 +300,000  + 2% 20.  Microsoft Live 25,100,000 +300,000  + 1%

Yahoo! Social Bar is an Open Graph integration that shares what articles users read on Yahoo. No. 4 Washington Post Social Reader also shares what users read, but the app lives in the Facebook canvas and as a standalone mobile app, not on WashingtonPost.com. Both apps are gaining again after a period of decline while Facebook made some changes to the way social reader stories appeared in News Feed.

No. 3 YouTube has doubled its Facebook-connected MAU, likely because more users are turning to the video sharing site to watch clips and live streaming of the Olympics.

A number of customizable page tab applications from Woobox made the list, as did mobile apps from HTC Sense and Samsung Mobile.

At No. 20 was desktop chat client Microsoft Live, which has seen a steady increase in MAU over the past few months.

All data in this post comes from our traffic tracking service, AppData. Stay tuned for our look at the top weekly gainers by daily active users on Thursday, and the top emerging apps on Friday.