Image from Smarterware.org

Favicons are the symbols that you see to the left of the address bar in your browser.  In Firefox, favicons also appear in tabs as well.  With Greasmonkey scripts or Firefox extensions, you can place unread item counts for Gmail and Google Reader right into your favicons, enabling you to see how many unread items you have without making a tab active.  Now add Google Voice to that list.  Gina Trapani's Smarterware blog has a link to a Greasemonkey script that brings favicon alerts to Google Voice.