Replacement for Command-Tab

Check out Witch. It is a great app(well, prefpane actually, that switches between apps as well as the documents related to the open apps(same kind of floating-window interface as Command-Tab, but better, in my opinion than Command-Tab). Try setting up Command-Shift-LeftArrow as the shortcut under Cycle Windows -> All Applications inside the Witch preferances pane in System Preferences. So, I hear Cmd plus ~ switches between all the documents of an app, but this seems to be a bit more convenient for me.