There isn't much for Notepad++, but I would recommend taking a look at JN-NPP. Installation can be done via the Plugins Admin by searching for the jN Notepad++ Plugin. It can also be done by just placing the DLL, and the includes, in your plugins folder in the Notepad++ directory (highlighted here).
One of it's main features is the Smart Highlighting, which is essentially what you are looking for (on highlighting of a word, all occurrences will appear as green lines on the right hand side).
It also has a slew of other features, such as JSHint (A tool that points out errors in JS code), CSSLint (cleans up CSS code), a basic SVN client, a music player (for some reason), and many others.