iPhone/iPod touch: Web-based Twitter client Brizzly is just like Twitter's website, except better in every way. Brizzly's free iPhone app is a similar experience upgrade, with web-synced lists and muting, news and search tracking, easy photo uploads and more.
So Brizzly's iPhone app, resulting from their purchase of Birdfeed, doesn't necessarily do anything that isn't covered by its web client, or some other iPhone Twitter clients. By providing a similarly stripped-down reading and writing experience that syncs with the web, however, it's got a strong selling point. Multiple accounts are supported, and if you're using Twitter to track a topic or something work related, you'll dig being able to make one of its main tabs a topic search. Gizmodo's gone so far as to call Brizzly the best iPhone Twitter client available right now; in this editor's opinion, we wished some of Birdfeed's interface grace was kept around, but that sounds about right.
There's no Facebook support in this app, but we'd hope it's on the way. Also, as with the web app, Brizzly's users contribute helpful, sometimes snarky explanations of Twitter's trending topics. The iPhone/iPod app provides these explanations in their own tab:
Brizzly is a free download for iPhones and iPod touch models running at least the 3.0 firmware.