Shortstack allows free, professional custom tabs for your Facebook Page - includes templates for Pinterest tabs, promotions & sweepstakes, customer details capture (opt-in), and more.
Create an ecommerce store within Facebook. Free service allows you to add your products (can be digital or service packages) to a store within your Facebook Page (custom tab)
URL shortener, for use in Twitter and other social posts and updates, which allows click tracking - how many people clicked your links? Bit.ly shows you what posts have caused the best reaction and engagement.
Buffer takes your tweets, and sends them at the optimal time - the time at which your followers have shown themselves most likely to see, share and clickthrough on links.
Sell & promote digital products, including audio, video and whitepapers/ebooks - integrates with Paypal, and allows you to discount your products if the buyer shares it via their networks
Roboform password management - this plugin for Chrome allows you to store your passwords in one location, allowing login to all your services from anywhere.
Just came across this one ... A place to keep your profile data (biog, etc.) that then sync's with all your social profiles, so you only have to change in one place! Genius!