GooSync has introduced a new, free beta service for synchronizing your Google’s Gmail calendar with any mobile device using the SyncML protocol.
You need to register for a free GooSync account. Then configure your SyncML client in Nokia, Sony Ericsson, Windows Mobile or Palm mobile device with the following settings-

Sync server URL: http://www.goosync.com/sync/sync.aspx
Username: Your Goosync UserName.
Password: Your Goosync password.
Calendar database: Calendar