Quicksilver, from BlackTree, is a handy tool to launch/browse apps/files, and with Leopard, it would be ideal if we could activate Quick Look on a file selected in Quicksilver. It turns out to be a fairly easy task to add this feature.
First create this shell script and save it as ~/bin/ql (remember to make it executable with chmod a+x ~/bin/ql):
#!/bin/bash
qlmanage -p "$@" >& /dev/null &
Next create the following AppleScript, and save it as QuickLook.scpt in ~/Library » Application Support » Quicksilver » Actions:
on open of theFile
set thePath to quoted form of POSIX path of theFile
do shell script "~/bin/ql " & thePath
tell application Quicksilver to hide
end open
Then quit and restart Quicksilver. Now whenever you select a file, you can choose a newly-added action named QuickLook to have a quick peek at the file.
[robg adds: I haven't tested this one...]

