As you may know, Indicator Stickynotes is a small app, that allows you to pin stickynotes to your Indicator bar, in order not to forget things. It works with Unity, Gnome Shell, XFCE, KDE, MATE and Cinnamon. It is similar to the yellow colored sticky note program, installed by default on Windows 7 or Windows Vista.

The latest version available is Indicator Stickynotes 0.5.6, which has been released a while ago, bringing updated translations.
Installation instructions:
Indicator Stickynotes is available via some third party PPA, so installing it on Ubuntu systems is easy. Just add the PPA to your system, update the local repository index and install the indicator-stickynotes package:
$ sudo add-apt-repository ppa:umang/indicator-stickynotes
$ sudo apt-get update
$ sudo apt-get install indicator-stickynotes
Optional, to remove indicator-stickynotes, do:
$ sudo apt-get remove indicator-stickynotes
The installation instructions should work on Ubuntu 15.10 Wily Werewolf, Ubuntu 15.04 Vivid Vervet, Ubuntu 14.04 Trusty Tahr, Linux Mint 17.2 Rafaela, Linux Mint 17.x, Pinguy OS 14.04, Elementary OS 0.3 Freya, Deepin 2014, Peppermint 6, Peppermint 5, LXLE 14.04 and Linux Lite 2.