PinsPro Pin-board Style Theme w/ Drag & Drop
Pinterest has been around for a few years now. It has millions of active users contributing to it on a daily basis. Other social networks such as Google+ are also allowing their users to create collections. You could always build your own collection site using themes such as the PinsPro. This theme is designed for WordPress sites powered by PageLines DMS.
The theme has a responsive design and lets you lazy load posts or allow your visitors to grab posts using a button. The pins are dynamically arranged. PinsPro is social media friendly and has over 50 drag & drop sections for you to use. It is coded in HTML5 and CSS.
PinsPro might not work for every website, but if you are interested in cloning Pinterest, you should give it a look. This is a commercial theme.