A few days ago I published the first version of Mappero Geotagger, an open source geotagging application for Linux, Mac OS X and Windows.
Geotagging a file means assigning a geographic location to it, and it's an action typically performed on picture files, so that the geotagged photo can be shown on a map at the location where it was taken. Many photo-sharing websites, like for instance flickr and picasa, will show your pictures on a map, as you can see for example in this picture of mine. Some services also allow you to view all photos taken in a certain area; for instance, here are some nice pictures taken in Porvoo, Finland.
Mappero Geotagger is a simple graphical tool to geotag your photos. You can manually move pictures on the map to set or change their location (removing the geotag is also possible) or, if you happened to record your way with a GPS while you took the pictures, the program can automatically correlate the time of the photos with the time of the GPS signal, and therefore establish with a certain precision where the pictures where taken. Since the time of the GPS receiver and the time of your camera might differ (and usually they do, especially if you travel to a different time-zone and forget to update the time in one of your devices), Mappero Geotagger has some controls to allow you to smoothly adjust the time difference and provides you an immediate feedback as you'll see the images being laid out on the map along the GPS track. The video below should give you a better idea of how this works:
See Mappero Geotagger in action
I'm selling the application from my website for 15€, but if you hurry up and either tweet or mention it in Google+ you can have it for 5€ only — and if you blog about it, you'll get it for free. Detailed info on the promotion are here
Incidentally, if you own a Nokia N9 or N900, the source code which you will get when purchasing Mappero Geotagger can also be compiled for these phones, into an application (still under heavy development, but already usable) which lets you record a GPX track usable with Mappero Geotagger.