I just wrote this script to convert traditional Chinese text to simplified Chinese. Since the relationship between traditional and simplified characters is many to one, I haven't decided to write the revert convertion script.
It has been tested with my files and can be downloaded here, and please report bugs and suggestions if you found any.
The package contains two files, simplify.py and utftable.txt. The python script is the converter and utftable.txt is the character table. The two files must be put into the same directory.
python simplify.py input.txt >output.txt
Both the input and the output text files must be in UTF8.
Note that you can replace the character relationship table file with your own file (the new file must be in the same format as the original file), just in case there are more comprehensive tables than this one.