If you can’t tell, I am a heavy user of Quicksilver. It is far superior to Spotlight for cataloging, searching and finding documents. If you are a Del.icio.us user then here is a QS tip to allow you to search your own bookmarks AND TAGS!
Select the “Del.icio.us” plugin from the preference window of Quicksilver
Now go to the preferences pane and choose “Catalog”
Add your delicious bookmarks as a new catalog