GCALDaemon is a Java program that offers two-way synchronization between Google Calendar and various iCalendar (RFC 2445) compatible calendar applications (Sunbird, Rainlendar, Apple iCal, Lightning, Evolution, KDE Kontact, Vista Calendar, etc).
Gmail Address Book browsing with Thunderbird
RSS/ATOM news reading with Sunbird
Gmail Address Book / LDAP provider
Google Calendar event modification with Mozilla Sunbird