Dad got a camera with built in GPS. The GPS info is embeded in the EXIF data, I guess. Picasa 3 puts a small "icon" on each of the geotagged photos, but can not do anything with them (as far as I can tell).
Is there any photo manager or mapping tool that can put these pictures on a map and/or let him browse trough the photos based on location?
Digikam is by far the best photo-management utility on Linux, and it does support showing a map with your photos on it.
See this related page for instructions on installing Digikam on Ubuntu 14.04.
GpsPrune can plot your local photographs on a map, modify the data and export it in KML and other formats for use with mapping services like Google Maps or OpenStreetMap.
sudo apt-get install gpsprune
You want GottenGeography. It will show the locations of your photos on an OpenStreetMap background. It also will allow you to map photos from cameras without a built-in GPS, either by manual positioning on the map, or correlating with a GPS output file based on timestamp.
According to this old post the present Digikam may be able to do what you want; http://scribblesandsnaps.wordpress.com/2009/11/03/geotagging-photos-with-digikam/, according to this post the soon to be released Digikam 2.0 will have even more advanced Geotagging features with the Reverse Geotagging widget, http://www.digikam.org/drupal/node/532.
I would say give Digikam a try to see if it will work for you now or if you will have to wait for version 2.0. Digikam is a very powerful photo management application available in the repositories.
You can use Geotag to do that. This is a Javatool to geotag Photos and see them on a GoogleMaps page.
It is not a photo manager, but it is easy to see your photos on a map.
Flickr handle geo tagged photos and is able to display them on a map. This is a web application and you need to upload your photos (2gb / month with a free account)
Privacy is a taking seriously and you have to adjust geotag settings because they are disallow by default.
I know this is not the kind of application you are looking for but this can help, Flickr is an excellent service to manage, backup, share ... your photos. I personally use it to backup all my photos.