If you post a lot of status updates, chances are you've found it annoying to have to post to multiple social networks. On top of being a pretty great Twitter app, TweetCaster can mirror your updates over on Facebook so you don't have to post them twice.TweetCaster offers many of the standard features you'd expect in a Twitter app, such as viewing and posting status updates, multiple accounts, lists, search, and so on. It also adds a lot of visual customisations, the ability to mute tweets (they call it "Zip It"), and threaded conversations (so you can keep track of replies more easily).
What's really handy is its ability to post to as many accounts as you want. That includes both Facebook and Twitter. You just have to add the accounts you want, type your message, and post it. That'll send your status to everything you choose at once.
This is a pretty good deal for free, but you do have to deal with ads if you're not paying. Upgrading to Pro comes at a steeper-than-usual price of $5.49 (our favourite iPhone Twitter client is only $1.99), but fortunately you have the option of a ad-supported version if that's too much for you.
TweetCaster (Free or $5.49 for no ads) [iTunes App Store]