Try SlingShot Application Launcher from Elementary Team in Ubuntu 11.04 Natty Narwhal

Elementary team has come up with their own application menu called slingshot which provides a pleasing and simple to use interface for browsing installed applications on your system.

Slingshot has not finished yet and is under heavy development but even at this stage it looks quite nice.

To install slingshot, run following commands:

sudo add-apt-repository ppa:elementaryart/elementary-dev

sudo apt-get update

sudo apt-get install slingshot-launcher

Please note that these packages are not stable but development builds.

To launch slingshot, run the command slingshot from terminal or create a launcher. Slingshot works in both Unity and classic desktop environment.

Here is a video (Watch in HD):