I am looking for a Gnome panel applet which can open and close the dvd/cd tray , I am on Ubuntu 11.04 and use Gnome Classic desktop environment.
I do not know any applet capable of triggering the cd tray, but you can add a custom launcher as applet.
eject -Tin the "Command" field.
This should work, but I could not test it, since I do not have a cd drive.
For detailed information about this command, type
man eject in a terminal.