BambooInvoice- Open Source Invoice Solutions

Simple and easy to use, this invoicing software sits on your server so you can control all your data securely and privately. It's highly customizable, including the ability to upload your own logos and images.

KTorrent - Open Source multi platform BitTorrent client

KTorrent is a bittorrent application for KDE which allows you to download files using the BitTorrent protocol. It enables you to run multiple torrents at the same time and comes with extended features to make it a full-featured client for BitTorrent.

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).

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.