iSync, MobileMe: About the Sync menu extra
In the Sync pane in MobileMe System Preferences, there is an option named "Show status in menu bar."
This option activates or deactivates the Sync menu extra. When you activate this menu extra, you can sync certain items from the Mac OS X menu bar, monitor sync status, and access advanced features like Sync Diagnostics.
The Sync menu extra animates when synchronizing certain data (Bookmarks, Calendars, Contacts, and so on). This menu extra also displays sync status for MobileMe and other devices, such as when the last sync occurred.
Additional information for Mac OS X v10.6 Snow Leopard
In Mac OS X v10.6 Snow Leopard, this animated notification also indicates iDisk Syncing. If you are using Automatic Syncing and iDisk Syncing, the Sync menu extra will frequently be animated due to the Push Sync activity of MobileMe Automatic Syncing and the synchronization of your local iDisk copy with the remote iDisk data stored on the MobileMe server.
The Sync menu extra is on by default after you have enabled MobileMe Sync in the Sync tab of the MobileMe System Preferences. The Snow Leopard version also allows access to Sync Diagnostics and Reset Sync History. Hold down the Option key to see these additional options when you click the Sync menu extra.
Note: Avoid unnecessarily resetting Sync History. Resetting Sync History from this menu extra, the iSync application, or the MobileMe System Preferences pane may cause the next sync to take much longer. See iSync Help for more information about this feature.