Yahoo! has released a desktop email and personal information management client called Zimbra Desktop. It's based on the Zimbra email, calendar, and contact service that Yahoo! purchased a few years ago for $350 million. And that explains why the desktop client looks so much like the latest version of Yahoo!'s web based email service.

The interesting thing is that Zimbra Desktop doesn't just provide access to your Yahoo! email account. You can also link it to your Gmail, AOL, Windows Live, or other web mail accounts. It supports POP and IMAP as well. If you're using a tag-based email service like Gmail, Zimbra Desktop will import your labels and treat them like folders. But you can also use the email client to tag, sort, or search for messages on your desktop.

Zimbra is an open source application and it's available for Mac, Windows and Linux. Not only does it have an integrated calendar and contact solution, but it can also import your calendars and contact lists from Yahoo! and Gmail. Windows Live address books can also be imported, but not the calendar.

Personally, I haven't felt much need to use a desktop email client for the past few years. Web mail is accessible from any computer with a web browser, as well as mobile devices. And you don't need to configure any software to get it working. But if you're a fan of desktop email clients, you might want to give Zimbra Desktop a look. It's free, after all.

If you have an opinion about the next open source master of the universe software company(ies) for 2008, you can vote for them and make your voice heard at Linux Magazine's annual top 20 companies to watch edition. Last year, Zimbra, (recently acquired by Yahoo for $350 million) XenSource (enterprise virtualization bought by Citrix for $500 million) and Canonical (think Ubuntu on Dells) made huge breakthroughs.

Nominate your favorites by October 30 and the finalists will be revealed in January.

Michael Arrington of TechCrunch is reporting that Yahoo! has paid $350 million to purchase Zimbra. The official announcement isn't expected until this evening, but Arrington's in a pretty good position to pick up gossip today. He's hanging out with a ton of industry insiders today at a little software conference Arrington put together with Weblogs Inc. founder Jason Calacanis called TechCrunch40.

So we're going to assume his information is good and enter the world of wild speculation.

Zimbra makes some impressive open source communication tools for online/offline use. The company has a powerful e-mail client, calendar, and VoIP features.

While it's unlikely that Yahoo! plans to completely overhaul its e-mail client yet again, we could see Zimbra features showing up in Yahoo! services. Particularly the slick AJAX interfaces, the powerful collaboration tools, and the online/offline functionality.