An Elementary OS launcher (slingshot) is application launcher like Mac OS application launcher which use in Elementary OS Distro (New Ubuntu Based Distro). First sight, slingshot seems like a application launcher that work on Unity but *in think Elementary OS Launcher has a better looks and appearance.
Elementary OS (Slingshot) Launcher

Elementary OS Launcher which named Slingshot is a Mac OS X style Launcher for Ubuntu and Debian Linux, much like JumpPad is for Windows. Elementary OS Launcher can be integrated to the Unity application Launcher to quickly access files and applications. See the below instructions to install and create a Unity launcher for Slingshot.

Install Elementary OS Launcher (Slingshot)
Follow instruction above to install Elementary OS Launcher (slingshot) on Ubuntu 11.04 :
 sudo apt-add-repository ppa:elementaryart/elementary-dev
 sudo apt-get update
 sudo apt-get install slingshot-launcher
Add Slingshot to Unity Launcher Application List
Create Unity launcher config file in /usr/share/applications/, follow this command  
 sudo gedit /usr/share/applications/slingshot.desktop
Add following line to file above, change the last line "Icon=path/to/your/icon", with path of icon that you prepare :

 [Desktop Entry]
For the last, open up nautilus file browser and navigate to /usr/share/applications/, drag and drop the slingshot shortcut icon onto Launcher.