GCALDaemon: Sync your Google Calendar
GCALDaemon [1] is an OS-independent Java program that offers two-way synchronization between Google Calendar [2] and various iCalendar compatible calendar applications. GCALDaemon is primarily designed as a calendar synchronizer but it can also be used as a Gmail notifier, Address Book importer, Gmail terminal and RSS feed converter.
GCALDaemon is released under Apache License version 2.0.
[1] http://gcaldaemon.sourceforge.net
[2] http://www.google.com/calendar/