GraSy

GraSy is a tool that converts context-free grammars, which are written in the ”Backus-Naur Form” (BNF), into syntax diagrams and the other way around. The grammar and the syntax diagrams can be saved with g2s-file. It is also possible to export syntax diagrams as PostScript files. To keep a good overview while creating syntax diagrams it is possible to change the zoom level. (Source: http://freecode.com/)