If you're looking for an 'app drawer' there is nothing that I know of that provides that graphical functionality alone.
For the ability to type in things to launch you have: gnome-do, kupfer, and synapse.
For an alternative to Unity, you can use Gnome-Shell from the gnome3 team that also supplies a similar 'app drawer' functionality. Of course gnome-shell is like unity in that it changes how you interact with your desktop.
But if you want to give it a try, I suggest building it from source, because it will allow you to fall back to your default desktop configuration if necessary without the hassles of needing ppa-purge. Note that building it from source may take a long time (over an hour)
Instructions here: http://www.webupd8.org/2010/10/install-gnome-shell-from-git-in-ubuntu.html