digiKam

digiKam is a free and open-source application designed to organize, edit, and view your entire image collection. It'll keep you from losing pictures amongst all the different folders on your hard drive and going mad whenever you go looking for one of them.

An interesting feature in digiKam is that it lets you preview all your photos directly from your digital camera, without having to move them to your computer or download/delete them. It can also import pictures from Facebook and Picasa, so you don't lose any of your albums.

Thanks to its comprehensive graphic editor, you can do a good number of things to your image, applying different filters and textures as well as using other tools to improve your photos.

All this makes digiKam a good choice amongst all the other photo-editing applications out there. It not only organizes your pictures and lets you view them, but also incorporates an efficient editor so you can create error-free images to share and be proud of.