Qt - Powerful, flexible and easy to use, Qt will help you not only meet your tight deadline, but also reduce the maintainable code by an astonishing percentage.
CpConverter - Code Page Converter - Convert HTML/Text files to different encoding formats e.g.
GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.
CONVERTCP - CONVERTCP is a command line utility to convert text file encoding.
wxWidgets - wxWidgets: Cross-Platform GUI Library
ConvertZ - ConvertZ is a program to convert Chinese/Japanese codes.