From the patch notes:
This weekend, July 1-July 2, we’ll be hosting a special Community Day to celebrate the new Twist Beta and the upcoming launch of TITANS! By participating in Community Day, you can earn 11 free packs within 24 hours! From July 1, 12:00 p.m. (PDT) to July 2, 11:59 a.m. (PDT), earn six drops, each for watching 1 hour of any Hearthstone stream.
First hour: 1 Ashes of Outland Pack + 1 Scholomance Academy Pack
Second hour: 1 Madness at the Darkmoon Faire Pack + 1 Forged in the Barrens Pack
Third hour: 1 United in Stormwind Pack + 1 Fractured in Alterac Valley Pack
Fourth hour: 1 Voyage to the Sunken City Pack + 1 Murder at Castle Nathria Pack
Fifth hour: 1 March of the Lich King Pack + 1 Festival of Legends Pack
Sixth hour: 1 TITANS Pack
Tune in to your favorite streamers and join them for this massive celebration of Hearthstone’s past and future! Make sure you link your Twitch and Battle.net accounts so that your viewing time counts towards drops.