I recently upgraded from 12.10 to 13.04 and I know that during the upgrade Ubuntu removed some of my indicator apps (weather app, Xpad, Artha dictionary, Banshee).
Can I still restore them on my system tray? How?
I think that the most easy way is to install them again by using Ubuntu Software Center. Just look for them again and install them.
Crossposted from another Ubuntu forum community, someone linked me to the steps on how get back the system tray whitelist.
From a Web Up8 post:
"Then, restart Unity by pressing ALT + F2 and entering "unity" or by logging out."
Dconf Editor > com > canonical > unity > panel > systray-whitelist
Additional reference: HOW TO RE-ENABLE THE NOTIFICATION AREA (SYSTRAY) IN UBUNTU, FOR ALL APPLICATIONS