Last week I mentioned that I use the GooSync Google Calendar synchronization service on my phone. As luck would have it I now have a premium account, with all the extra bits and pieces available to me - I could tell you how I got it, but then I'd have to kill you ;)
As I said before, basically what GooSync allows you to do is keep your Google Calendar and you phone's calendar up to date. It makes use of the phone's built-in synchronization abilities, and simply provides a new synchronization source. With a free account it is possible to sync with your default Google Calendar (from a Google domain or your own Google domain), in a window reaching 7 days into the past and 30 days ahead. All day events, timed reminders and recurring public and private events are synchronized both ways.
Synchronization happens through Google's secure API, so as part of the signup process you are directed to Google to authorize the service to access your calendar. Thanks to Google's spiffy access control, they don't get access to anything else at all.
In addition to the standard functionality, the premium service offers the ability to modify the sync window up to a year in the past and ahead. It also allows synchronization with multiple Google calendars, including shared calendars. Events from secondary calendars may be prefixed with a tag, so for example events on my Birthdays calendar are prefixed with [bday], while those from the (crucially important) South African Public Holidays public calendar have a [hols] prefix. Finally, attendee information is synchronized as well, though I have not been able to figure out how to view it on the n95.
The upgrade price of $19.95 might be a bit much for the casual Google Calendar user that only uses a single calendar (and even then only rarely). For someone that uses multiple calendars, shared calendars and is constantly trying to convert everyone and their dog to gcal to make their own lives easier (yes, like me) it's worth considering.