Enable Tray Icon For All Program In Natty Narwhal
You won't see tray icons for application that doesn't use app indicator.
To enable tray icons in Ubuntu 11.04 Natty Narwhal you can run the following command in terminal:
gsettings set com.canonical.Unity.Panel systray-whitelist " [ 'all' ] "
It will white list all the application for tray icon.
If you want to enable tray icon in only some of the application you can use:
gsettings set com.canonical.Unity.Panel systray-whitelist "['Wine', 'Dropbox']"
Here it will enable tray icon for Wine and Dropbox.