There’s no shortage of free iPhone Twitter apps out there, but newcomer Twizzle [iTunes Store link] certainly deserves a little bit more attention than it’s been getting.

The iPhone app has a slick, minimalist interface which is easy to use, and features a couple of options found only in paid Twitter apps.

Launching Twizzle takes you to a page where you can add your Twitter accounts. Other than Tweetdeck, this is the only free iPhone app that supports multiple accounts, and it does it much better.

Once you’ve entered your credentials, you can instantly access your Twitter timeline, mentions, direct messages, and favourites. You can also easily access your own or other users’ profiles.

When left open, Twizzle automatically updates your timeline. If you’re impatient, there’s a refresh button cunningly hidden out of sight, just above your timeline ““- drag your screen down, and the button will appear.

Tweeting from Twizzle is no different from other iPhone apps. You can include a photo from your photo library, or take a new photo with your camera and upload it to Twitpic, yFrog or Posterous. Choose which service you’d prefer to use in the app’s settings. For some odd reason, photographs uploaded to Twitpic all appear as landscape photos, regardless of how they’ve been taken. Accessing a photo, or any other website for that matter, opens it up in Twizzle’s integrated browser.

If your tweet exceeds 140 characters, and you click ‘Send’ anyway, Twizzle will prompt you to post it with Twitlonger, a service which adds a link to the end of your tweet, which users can click to read the rest of the text. Despite the inclusion of Twitlonger, it doesn’t include a basic link-shortening service, although we’ve been told this feature is on the developer’s to-do list.

From a user’s profile page, by clicking  the button in the top right hand corner, you can follow or unfollow them, send them a public reply or a direct message.

Twizzle’s organization of DMs is very handy, sorting them by username rather than in chronological order. DMs are nested, and are reminiscent of the iPhone’s SMS feature. To reply to a DM, open it up, and click on the pencil button at the top right hand corner of the screen.

One way Twizzle excels is its ability to handle threaded conversations. Open a tweet and click on the button marked ‘in reply to’ and it lists the entire conversation in chronological order, with the most recent tweet first. Twizzle’s threaded conversations are similar to those found in the paid app, Tweetie.

Twizzle’s search bar is conveniently placed at the top of your home page, for easy access. Clicking in the search bar will also give you reveal a link to Twitter’s latest trending topics and your saved searches. To open them, click the bookmark button on the top right hand corner of the screen. While there’s no way to save a search on Twizzle, it syncs with Twitter’s web-based saved searches. Hashtags used in tweets can be clicked in Twizzle, automatically opening a search page for that term.

Other features found in Twizzle are the ability to add or remove tweets from your favourites, landscape tweeting (a feature seen only paid apps such as Echofon Pro and Tweetie), as well as three different themes.

Try out Twizzle and let us know what you think of it in the comments. What are your favourite Twitter clients on the iPhone?