This Mac OS X hint shows how to use Quicklook from inside Quicksilver. I'm a big Quicksilver fan, but frankly didn't get very excited since just hitting "return" launches Preview as fast as hitting "tab->q" and then waiting for the AppleScript to run. But, along the way, part of the hint involved creating a small shell script:
#!/bin/bash qlmanage -p "$@" >& /dev/null &
Using the script, you can launch QuickLook from the command line. Now that's handy!
qlmanage is a very chatty program that performs operations on the QuickLook cache and generators. I saved the above script as ql.