To install RapidLauncher you will need to have GTK+ 3 and its Vala bindings installed.
On Ubuntu (12.04) these packages are called:
gir1.2-gtk-3.0
libgtk-3-dev
When you have all dependencies installed simply run the install.sh script, which will interactively ask you for your requirements, set the environment variables accordingly and run make.
$ make
$ sudo make install
Once you have installed RapidLauncher you can start it with the 'rapidlauncher' command or by using the included .desktop file.
You probably want to bind the rapidlauncher
command to a keyboard
shortcut.