Sync'Em is a multi-sync hub for Macs that's designed to sync Microsoft Exchange, Google and Apple contact and calendar information.
Sync'Em is unique in its ability to multi-sync -- sync multiple configurations, each involving multiple information sources with each syncing bidirectionally or unidirectionally.
Sync'Em has its own full-featured sync engine that syncs non-Apple sources directly, enabling it to sync Exchange-to-Exchange, Exchange-to-Google and Google-to-Google and perform multi-source conflict resolutions in one interaction.
Sync'Em can be downloaded via http://www.syncem.com/SyncEm-Download and requires Mac OS X 10.4 or 10.5. 15-day 2-Mac full-featured Trial licenses are free and all version 1.x updates are free to registered owners.