I haven't found the feature where i can publish my Google Calender to a specific URL, which can be done at 30 Boxes. Here's my calender on 30 Boxes. 30 Boxes also features a RSS feed, that is quite handy. Oh, talking about that: that's exactly what RSSCalender does, which was featured here before.
So, in conclusion: I haven't decided yet which one is the winner for me. I will let you know which online calender I prefer, when I am ready exploring.