APIs

Spotify - Music

Google Mirror API - Tools

TradeKing - Financial

Tumblr - Blogging

Instagram - Social

YouTube - Entertainment

Coinbase - Financial

AngelList - Tools

Streak - Enterprise

Sincerely Ship - Photos

App.net - Entertainment

Paypal - Financial

Twilio SMS - Messaging

Google Maps API - Maps

Twitter - Entertainment

Evernote - Tools

Dropbox Core API - Storage