How to implement georeferencing in Drupal? I must make a website with geo-referenced content. And I would like to add POI and the possibility to download this POI for GPX, KML\KMZ (Google Earth), etc.

Any tips or ideas to implement this somehow?

PS: if the above is not clear enough, have a look at this or this (the idea is building a website with such contents).
If you want to use an existing module - something like GMap is probably the easiest place to start.

That being said, the Google Map API is fairly easy to use, so nothing preventing you from writing a module that does exactly what you want.