If you&'re setting out to design a new website, there are few better starting places than a wireframing service: they let you quickly get a rough idea of what your site will look like, without having to deal with paper cut-outs or endless pencil erasing. And today, one of the better wireframing services is leaving beta with some major new features in tow for its official launch. Meet Mockingbird.

The bootstrapped, two-person startup launched around a year ago, offering a clean interface that&'s based on the Cappuccino web framework (in other words, it isn&'t in Flash, unlike many of its competitors). Since launching in a beta it&'s grown to 55k users and nearly 100k projects created.

Today, Mockingbird is launching real-time collaboration, which means that multiple people can fire up their web browser (no install required) and start editing the same page layout. This is obviously a big deal given the collaborative nature of design, and in practice it looks pretty slick (you can see it in action in the video below, or you can check out the demo page to try it for yourself).

The other big change with this launch: Mockingbird is ready to turn on the revenue faucets, and will start charging for its more robust plans. There&'s still going to be a free version available that supports 1 project with a maximum of two users, and premium plans start at $9 a month.

Competitors in this space include Balsamiq, which offers a desktop application rather than a web app, Mockflow, Hotgloo, and a nifty iPad app called iMockups.

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