Later - Schedule and manage your Instagram posts
Retweet Picker - Retweet Picker is an online tool that is helping you to select the random winner from Twitter for the giveaways.
Grum - Post on Instagram from your computer!
Tweetdraw - Tweetdraw is an online tool that provides an easy way to pick a winner for a giveaway, having a quick Twitter Quote Draw, Instagram Comment Draw, and Twitter Retweet Draw.
Uplet - Uplet is an easy-to-use bulk Instagram uploader for Mac.
Twesocial - Twesocial helps you grow your twitter with real twitter followers. Real results, real people.