Seesmic just announced the launch of Twitter lists in its browser-based Seesmic Web Twitter client. Earlier this week, Seesmic released the first desktop Twitter client with support for lists. Despite Seesmic’s best efforts, Brizzly managed to become the first company to release a web client with support for lists earlier today. Seesmic Web offers another first for web-based Twitter clients, however: support for Twitter’s geolocation API.

Lists With Auto-Updates
In Seesmic’s web interface, users can now simply hover their cursor over profile pictures and a menu will appear. This menu, among other things, allows Seesmic’s users to add others to lists. One nice aspect of the web interface is that it auto-updates lists when new tweets come in. The desktop app – at least in the current version – doesn’t do this and forces users to manually refresh lists to see updates.

Geolocation
In addition to supporting lists, the new version of the web client also supports Twitter’s geolocation API. Seesmic users can’t share their locations, but whenever a Twitter user broadcasts location data, a little pin will appear underneath the profile picture, and hovering over this pin will bring up a map. Only a few users actually have the ability to broadcast their locations at this point. Twitter is only giving platform developers access to this feature for now, but it should soon become a standard feature in mobile clients like Tweetie 2 and Twitterrific.