F-Spot – Open Source Mail Transfer Agent

F-Spot is an image organizer, designed to provide personal photo management for the GNOME desktop environment. The name is a play on the words F-Stop and G-Spot.
F-Spot aims to have an interface that is simple to use, yet still supports advanced features such as tagging images and displaying and exporting Exif and XMP metadata.

Digikam – Open Source Photo Management

digiKam is an image organizer and editor that uses the KDE Platform.
digiKam provides functions for organizing, previewing, downloading and/or deleting images from digital cameras. Basic auto-transformations can also be deployed on the fly during picture downloading. In addition, digiKam offers image enhancement tools through its KIPI (KDE Image Plugins Interface) framework and its own plugins, like red-eye removal, color management, image filters, or special effects. digiKam is the only free photo management application on Linux that can handle 16 bit/channel images. Digital Asset Management is the mainstay of digiKam.

Open Source Security Tool

PeerBlock is an advanced IP blocking utility

PeerBlock lets you control how your PC interacts with other computers over the Internet, letting you block servers and sites known to be troublesome or even dangerous. It lets you choose what to block, and you can also import or create your own lists.

TrueCrypt - Open Source System Security

TrueCrypt is a Free open-source disk encryption software for Windows 7/Vista/XP, Mac OS X, and Linux. It can create a virtual encrypted disk within a file or encrypt a partition or (under Microsoft Windows except Windows 2000 and Windows 8 with GPT) the entire storage device (pre-boot authentication).