The last few months have seen a big expansion in the scope and quality of desktop applications available for Facebook. The latest is a new version of Seesmic’s client, released today, that lets you interact with Pages you’re a fan of or administrator of without having to go to Facebook’s site.

This feature could be especially useful for people trying to track the latest updates about particular organizations, such as marketers and journalists. Seesmic already lets you read and reply to Twitter and Facebook from its desktop app. But neither it nor any other desktop has offered as many ways to interact with both Twitter and Facebook.

With the Pages integration, you can pick out Pages you’re already a fan of from within the app’s account settings. Toggle any page you want, hit save, and it will appear in the app’s left-hand menu. Click on a particular page and you’ll open up a new column in the app showing you all of the latest updates. You can post messages and respond to Page comments from within the app.

This desktop interface offers a faster-updating, more responsive interface for Facebook’s pages than using the company’s own site. Seesmic is also introducing some features for Twitter today, including a reply-all button for tweets mentioning multiple users, a timeline of “favorite” tweets, and a partnership with image-hosting company Yfrog. In total, the app has been downloaded more than 2.5 million times.

Seesmic is not the only desktop app to come out with some slick Facebook integration.

Today, Digsby rolled out a new version of its social media desktop client to include integration with basic Facebook features, as well as chat integration. The app now lets you chat and message across a wide variety of social networks, IM and email services.

And perhaps Seesmic’s biggest rival, Tweetdeck, also just launched a new version of its Facebook integration. Last week, the company introduced new ways to drag and drop photos and videos, add comments and likes, and create different groups of Facebook friends to follow.

Finally, Facebook itself has rolled out its own desktop apps of sorts, most recently introducing a new version for Mac as part of its launch of Prototypes.