I have wanted to Quick Look files directly from the browser for a while (especially .doc and .ppt files). A switch to Firefox recently exacerbated this problem, as there is no PDF plug-in. So I wrote a simple script that monitors the Downloads directory and opens any new files with qlmanage, and thought others might find it useful. Copy and paste the code below into a file (say ql_downloaded.sh) and make it executable (chmod a+x ql_downloaded.sh). Launch the script in a separate Terminal window, then start browsing.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20080318151932894