What does this mean? You can now fully (bidirectional) sync your Google Calendar with Apple's iCal or Mozilla's SunBird without using expensive applications like Spanning Sync or CompanionLink for Google! What it means for ME is that now I can sync my iPhone with Google Calendar (albeit not without syncing it with my Mac). So long NemusSync, for now.
Instructions for iCal can be found here, or read on:
Simply open iCal (currently version 3.0.4 build 1263) and open it's preferences (?+,). Go to the Accounts tab and click the plus sign under the (empty?) list. The description is up to you, but the username and password have to be your full Google login (ie: firstname.lastname@example.org or if you use Google Apps email@example.com). To make things work, the key trick is to click the arrow for server options and enter the specific Account URL for your calendar: https://www.google.com/calendar/dav/calid/user and ONLY change the calid. CalID is your calendar's name inside Google, and if you only have one main calendar it will probably be the same as your login.
A useful example (for those in the U.S.) would be to use
(note: you will still need to use a valid login).
Hooray for Google!