gThumb is a lightweight Linux photo organizer that is preinstalled on some distros. If gThumb is not installed on your Linux computer you should be able to install it through the package manager. I prefer this program over the Shotwell Photo Manager on Ubuntu because it behaves more like a folder browser. I do not use the program as my default image viewer however, preferring to use the Image Viewer program instead.
gThumb is great for importing images from devices and web programs such as Facebook or Flickr and it can also export your images to those locations as well. Once the images are imported you can resize them, edit the colors, crop, and do a few other small edits. The program has more editing options than the Image Viewer, but not as much editing potential as GIMP.
This is a must-install for any Linux user who wants to organize photos both on the computer and through web apps.