I have some applications like eclipse, netbeans, vuze extracted to /opt/ directory. These applications don't show up while searching in unity dash. Is there a way that I can get these applications indexed?
('run a command' does remember the paths after the first time, but pressing the Super button is easier than alt+f2)
You'll need to create a .desktop-file for it and place it in either /usr/share/applications/ to make it system wide or ~/.local/share/applications/ to add it for your user only. To get an example of what the file should look like, including quicklists, see this answer: What Custom Launchers and Unity Quicklists are available?. You'll just change the name, comment, exec, icon and add optionally add some quicklist entries.