What Application Indicators are available?

Solution 1:

System Load Indicator

Category: System Information

Network, memory and cpu usage indicator; this is a port of the original System Monitor GNOME Panel applet (gnome-system-monitor applet).

In Preferences you can customize the output to fit it to your desktop theme:

To install:

You can install it through the Ubuntu Software Centre by clicking this button:

or through the command line:

sudo apt-get install indicator-multiload

If you want the latest updates, you can install it from the PPA with these commands:

sudo add-apt-repository ppa:indicator-multiload/stable-daily
sudo apt-get update
sudo apt-get install indicator-multiload

Solution 2:

StackApplet

Category: Other

StackApplet is a GNOME panel applet that monitors your activity on any StackExchange site.

stackapplet in Ubuntu Software Center

For Ubuntu 12.04 to 14.04:

Get the latest version as follows:

sudo add-apt-repository ppa:stackapplet-dev/stackapplet
sudo apt-get update
sudo apt-get install stackapplet

The first time the application is used, run

python /usr/share/stackapplet/stackapplet.py &

from a terminal.

Solution 3:

ClassicMenu Indicator

Category: Application starter

Provides a simple way to get a classic GNOME-style application menu for those who prefer this over the Unity dash menu. Like the classic GNOME menu, it includes Wine games and applications if you have those installed.

To install Classic Menu indicator in Ubuntu Trusty Tahr:

sudo add-apt-repository ppa:diesch/testing
sudo apt-get update
sudo apt-get install classicmenu-indicator

Get the most recent version from its web page (PPA available for Ubuntu 11.04, 11.10 and 12.04).

Solution 4:

Hardware Sensors Indicator

Category: System Information

Application Indicator showing hardware sensors.

First add the repository:

sudo apt-add-repository ppa:alexmurray/indicator-sensors 

Update:

sudo apt-get update  

And then install the package:

sudo apt-get install indicator-sensors

Then launch Hardware Sensors Indicator from Unity or run indicator-sensors from a terminal.

Solution 5:

Weather Indicator

Category: Weather Forecasting

Warning. This indicator is not being updated anymore and will probably not work in current versions of Ubuntu.
UPDATE ! Development continues! https://launchpad.net/weather-indicator/+announcement/11516

Displays the current/extended weather, multiple locations and notifications support.

indicator-weather in Ubuntu Software Centre

or project's PPA: ppa:weather-indicator-team/ppa
Please note! The latest builds of Weather Indicator require updated versions of pywapi, Python Weather API: ppa:pywapi-devel/ppa