These are some tools that can make your experience on 4chan more enjoyable/easy to use.
This is a script that has much more functionality and options than the default pluing that was introduced to 4chan not too long ago. While this is a fork of the original 4chan X script, it has a few useful additions, such as; embedded video, linkify, more extensive filtering options, and is updated often.
This is another script that allows for a much more modern interface, with many options. There are several themes to choose from, and the layout is customizable (with or without sidebar). A must for anyone who frequents any boards. It also allows custom CSS editing and is useful for anyone who likes to edit the page that way.
Appchan X is a script which is designed to seamlessly combine the above plugins while adding its own features as well. It allows for everything from in-line image expansion to theming to the ability to only display posts with images (guess what that's designed for) and has tons of great themes built into it, also giving you the ability to make your own if you want. It is also updated pretty frequently, and is consistently having new features added. See the full list here.