Yahoo! has launched an open source desktop application “Sideline,” built with the Yahoo! User Interface Library (YUI), and Adobe AIR. It allows users to create and group custom queries by topics of interest. Sideline is a Twitter monitoring tool, giving you the opportunity to stay on top of the latest trends on the microsharing service and/or keywords you feed into the application. It has an auto-refresh feature (which you can tweak to have the search results reload between 1 minute and 1 hour), a notification system that alerts you of new keyword mentions in an overlay that appears whatever you’re doing and the ability to only look for favorited tweets containing the keywords you’re tracking. The first beta release is out and the code is hosted on github.