Insanely Useful Persistent Searches in GMail.

Using the Persistent Search Greasemonkey script for Gmail, Matt shows how to take advantage of persistent searches to create what amount to smart folders in Gmail. Persistent searches work differently than, for example, using filters and labels, because you can use operators like is:unread, is:starred, and label:inbox to make these new folders dynamic, in ways that labels are not.

Three solid Gmail productivity tips [Matt Cutts ]