Thunderbird is a total redesign of the Mozilla mail component to produce a cross-platform, stand-alone mail application using the XUL user interface language. It has many new features, among them the ability to customize your toolbars the way you want them. a new look and feel with a large number of downloadable themes which alter the appearance of the client, and the ability to add UI extensions.
aria2 is a utility for downloading files. The supported protocols are HTTP(S), FTP, BitTorrent, and Metalink. It has a powerful segmented downloading ability, downloading a file from multiple sources and multiple protocols and utilizing your download bandwidth to the maximum. It supports downloading a file from HTTP(S)/FTP and BitTorrent at the same time, while the data downloaded from HTTP(S)/FTP is uploaded to the BitTorrent swarm. Using Metalink's chunk checksums, aria2 automatically validates chunks of data while downloading a file like BitTorrent.
KMid2 plays MIDI and karaoke files to hardware MIDI devices or software synthesizers. It supports playlists, MIDI mappers, tempo (speed) control, volume and pitch (transpose) controls, and configurable character encoding, font, and color for lyrics. The graphic views include a rhythm view (visual metronome), a channels window with solo/muting controls and instrument selectors, and a piano player window (pianola).
KeePass is a light-weight and easy-to-use password manager that removes the need for you to remember many different passwords and makes it more feasible to use different passwords for each account. It manages your passwords in a secure database encrypted with AES and Twofish, which is locked with one master key or a key file.
Bitcoin is a peer-to-peer electronic cash system that is completely decentralized, without the need for a central server or trusted parties. Users hold the crypto keys to their own money and transact directly with each other, with the help of a P2P network to check for double-spending.
The cdcat is a graphical (Qt based) multi-platform catalog program that scans the directories/drives you want and memorizes the filesystem (including the tags of MP3s) and stores it in a small file. The database is stored in a gzipped XML format, so you can hack it, or use it if necessary. Cdcat can store the contents of some specified files up to a size limit if you want (for example: *.nfo).