rwdaddresses is a simple little address book program using flat files. In addition to text data, contact photos can be added and viewed. You can sync contact names to/from an FTP site. It has context sensitive help. Additional applets can be downloaded. The GUI interface used is RubyWebDialogs, which runs through a Web browser. Therefore, it is completely cross-platform. This is part of the Tinker framework using Ruby, so applets can be added and removed.