I've got several georeferenced digital photos as jpg, kml, and kmz. How can I import them into my GIS projects (QGIS or ArcGIS for Desktop) so I can open them as a popup?
If you are talking about GeoTagged photos, I'll recommend ArcPhoto, available at http://resources.arcgis.com/gallery/file/geoprocessing/details?entryID=8C3643DC-1422-2418-8836-CF0510413D40
This plugin can be considered an upgrade of the already existing and very good photo2shape plugin (http://hub.qgis.org/projects/photo2shape), developed by Alexander Bruy. The Geotag and import photos plugin was developed by Alexander Bruy and funded/designed by Giovanni Manghi and Lolita Bizzarri to respond to a specific task: manage, display and analyze photos obtained from photo-trapping surveys of wildlife.
If it's already georeferenced, for ArcGIS you could just import it as you would any other raster layer. If you need to georeference it, follow this in the helpfile:
If it is photographs rather than aerial photos, then follow this helpfile about adding HTML links/attachments to a feature class:
Now that I better understand your question, I think this is exactly what you wanted. :)
You can also use the ImportPhotos Plug-in: https://plugins.qgis.org/plugins/ImportPhotos/