There's a new Linux competitor to QuickSilver in town. It's called GNOME Do, and it just reached version 0.5.
It offers the same quick keyboard shortcut commands that QuickSilver does. Noun-verb-directobject goodness abounds.
If you've never used QuickSilver on the Mac, use it for a week, and you'll never be the same again. The keyboard takes on a whole new power.