Here is my situation. I get mails all the time about future dates of events. I try to be good and add them to my calendar but alas I sometimes fall short. When I do add events to iCal I then needed to share this through Google Calendars (gCal). Transferring to gCal was a pain at times. I tried going from gCal TO iCal but that was just as much a pain. Yes I know there is software to do this but up until now cost $$$ and I am cheap! There were some free alternatives but too geeky at times for me.
First big thing. Updating from Apple Mail. If you get an email with a date for an event you can simply click on it to add it to iCal. It can even guess the event title from the subject of the email.
So two clicks and it is now in your iCal. But how to get it to your gCal? Enter Calaboration. This FREE utility pushes your iCal to Google and from there it can be shared or subscribed to. For this you need only a free Google Account.