There are so many events for Magento developers and enthusiasts out there that it is difficult to keep up with all of them. That is why I created a publicly available Google calendar, which contains all Magento events around the world.
It shows all the events as full-day events, since most of them are just that. You can find the location in the respective field and the link to the (english) website in the description of the event. I hope you find it useful. If any information is incorrect or any event is missing, feel free to drop me a note.
By the way there is also a map of all Magento events around the world by AheadWorks, but it seems to be not really up-to-date. You can also have a look at the map in full size.