ExpressionEngine-1.6.x-Parse-Filedir-Plugin is a project mainly written in PHP, it's free.
Parses the {filedir_#} value that it gets passed. Useful for areas like looping through category descriptions that contain these tags.
Will take a file upload directory and return its path. Useful for things like category descriptions where these are not currently parsed.
{exp:parse_filedir}
{filedir_#}
{/exp:parse_filedir}
Will return /path/to/filedir/