Yahoo! has launched a new application called SIdeline that lets you keep track of trends and search terms in Twitter from your desktop. In a nutshell, Sideline is an Adobe® AIR™ desktop application built with the Yahoo! User Interface Library (YUI). It allows users to create and group custom queries by topics of interest.

Besides the ability to search terms and see messages from all Twitter users using those terms, you can also create Search Groups with the combination of multiple terms. e.g. “online streaming”, etc. If you would like to keep track of all the popular topics, there’s also a Trends area where you can check out popular topics across the Twitter network at the moment.

Sideline is an open source application released under the BSD license. The first beta release is out and the code is hosted on github.

Yahoo! Sideline : Watch, search and monitor twitter timeline