Two interesting lightweight launchers for Linux came across my radar today:
There is a Debian package for the Verve plugin named
xfce4-verve-plugin, which is part of
<Super> space in your Xfce keyboard settings
and you have a lightweight easy-access command-line with quick
activation along the lines of Spotlight in OS X
(there’s no search functionality, just command execution).
There is a package for Synapse in Debian Wheezy (current testing)
synapse. It’s heavier than Verve, aiming to be a
replacement for Gnome Do.