Seesmic Desktop Adds Twitter Lists, Hits 3 Million Downloads

Now that Twitter has officially unveiled its Lists feature to all users, the frenzy has started. But while Lists are available via Twitter’s site, the feature has been slower to come to Twitter clients. Today, Seesmic is announcing the availability of Lists on its desktop client, Seesmic Desktop.

The new, downloadable version of Seesmic Desktop will display your Twitter lists in the left sidebar from any Twitter account you have (Seesmic lets you use one client for multiple accounts). The new feature also lets you add any Twitter user to any user list from any of your account. Right now, list functionality is limited. You cannot see lists that list you, only lists that you follow. And you cannot create lists from the client; this must be done within Twitter’s site. But, Seesmic’s founder and CEO Loic Le Meur told me that both the ability to create lists and see lists that follow you will soon come to Seesmic Desktop in the next few weeks.

The list feature will also come to Seesmic Web shortly, says Le Meur. He also said that lists took so long to incorporate into the clients because the updated, comprehensive API wasn’t available until a few days ago. Le Meur and his team have scrambled to launch a new version of the desktop client over the weekend and will unveil it to Seesmic members today, and to the general public within the next few days. Other third party sites have also tapped into the Lists API, Listorious, a Lists directory.

List descriptions, which will be coming in the next week or so according to Twitter’s Vitor Lourenco confirms, would also be a valuable addition to clients like Seesmic.

TweetDeck, one of Seesmic’s main competitors, is also adding list functionality very soon, according to TweetDeck’s founder and CEO Iain Dodsworth. While the nature of TweetDeck’s lists feature is still a secret, he told me that “integration will be extensive and offer complete flexibility to TD users with particular emphasis on curation, consumption and portability of lists and existing TD groups.”

Seesmic Desktop, which integrated with both Facebook and Twitter, has also hit 3 million downloads, with the last 500,000 downloads taking place within the past month and a half. The client was recently upgraded to add Facebook fan pages, yFrog integration, a “reply to all” button for messages and a favorites timeline. Earlier this summer, Seesmic recently launched its browser-based Twitter client at TechCrunch’s Real-Time Stream CrunchUp. Seesmic Web will also be integrated with Facebook within the next month as developers are currently tweaking the application’s functionality on different browsers.

Disclosure: TechCrunch editor Michael Arrington is an investor in Seesmic. I am not.