Twhirl is owned by Seesmic, but the company's two desktop apps bear little resemblance to one another. Where Seesmic Desktop's interface is sizeable, Twhirl's is tiny: this small app looks more like an old-school IM client than a social media management tool. But it packs in plenty of features for managing your Twitter account: It automatically shortens posted URLs, notifies you of incoming messages, lets you search tweets, and allows you to record and share videos using Seesmic Video.
Note: This link takes you to the vendor's site, where you can download the latest version of the software. This program is donationware. It is free to try, but the author accepts and encourages donations towards further development.