The latest Leopard release has arrived, if you haven't already heard. Version 10.5.4 contains mostly security updates and bug fixes. However, AppleInsider points out that this version of Leopard also includes a "precursor" to support for the soon-to-come MobileMe, which has been touted as a replacement for .Mac.
According to Engadget, MobileMe enables users to store e-mail, contacts, calendar information online -- or "in the cloud," if you will -- and then "sync them to your iPhone." It's Ajax-based and will work with Mail.app, iCal, and the Mac address book, among other things.
The MobileMe Web site indicates the service will be available soon, but offers no further details. Subscriptions are available for individuals and families, with additional storage options also available.