If you’re planning on creating a Pinterest-like layout for your website, you can save yourself a lot of time and headache by using Masonry. It’s a cascading grid layout library that will let you get the elements in their best positions without a lot of trouble, leaving you spare time to focus on more important things (like taking a break).
If you want to integrate charts on your website, you should definitely take a look at Highcharts. They’ve got a very lightweight JS library that does all the work of converting data to beautiful graphs and charts, which can be customized quite extensively. Together with interactive actions and annotations, Highcharts is right up there with Google Chart Templates quality-wise, with the benefit of being self-hosted.
The downside is that Highcharts is only free for personal use – it’s worth the investment in my opinion, but if you want to save money on a commercial project, you might want to look for a completely free solution like JSCharts (which has improved significantly in the past few years).
Mobile devices are all the rage, and if you’re not optimizing your website/app for mobile, you’re losing out on a lot of potential users and customers. HammerJS can help you with that – it makes implementing touch gestures much easier, and they will probably be more advanced than any custom solution you can cook up in a limited timeframe. Panning, Pinch, Rotation, Single/Double/Triple taps – HammerJS offers it all in a small package that is ready for work with a few CLI commands.
Backbone works its miracles on the back-end, and lets you add significant functionality with ease. The library (well, it’s more akin to a framework, but still fits the definition of a library) provides key value binding and custom events for your models, a rich API for collections, declarative event handling for views, a RESTful JSON interface for existing APIs, and more.