Microsoft seems set to debut its newest addition to the Windows Live family, a calendaring application, and is also preparing to bring several Live services out of beta, sources report.

LiveSide.net is reporting that Windows Live Calendar briefly made an appearance on Microsoft's servers, apparently for testing. It's appearance led the site to believe that a release is imminent.

Noted Microsoft pundit Mary Jo Foley later cited sources that were pointing to a release today, although as of press time the site had still not gone live.

Either way, the addition of the latest calendaring application would mean the Redmond company has at least four major datebook apps, including an MSN-branded one as well as those within Windows Vista and its Outlook productivity suite.

It is not clear whether Windows Live Calendar is intended to eventually replace it's MSN counterpart, although past actions by Microsoft would likely mean the MSN service will be folded into the new product. However, in any case, the calendaring application has spent a long time in development.

Rumors of Windows Live Calendar first appeared in 2006, and a Live team member told Foley in May 2007 to expect it over the summer. However, for whatever reason, the application never surfaced.

Live Calendar is expected to mesh with other Live services -- the hallmark of the concept -- however it appears to be not much more than an incremental upgrade over the already-available MSN version.

According to Foley, the week could also bring a host of Live apps out of beta, as well as introducing several new ones. Among the possible releases are Windows Live Photo Gallery, Writer, Parental Controls, SkyDrive, Messenger, Events, and Hotmail.