Archi is a free, open source, cross-platform tool and editor to create ArchiMate models.
ArchiMate is an open and independent Enterprise Architecture modelling language that supports the description, analysis and visualization of architecture within and across business domains. ArchiMate is one of the open standards hosted by The Open Group and is fully aligned with TOGAF2.
Archi is targeted toward all levels of Enterprise Architects and Enterprise Modellers. It is intended to provide a low cost to entry (i.e. free) solution to users who may be making their first steps in the ArchiMate language or who are looking for a cross-platform ArchiMate modelling tool for their company or institution. Archi fulfils the needs of most Enterprise Architects and associated stakeholders, but it can also be regarded as an introductory ArchiMate tool for those wishing to engage with the language before committing to a commercial solution.
For more information on ArchiMate see:
http://www3.opengroup.org/subjectareas/enterprise/archimate
The main Archi website:
All developer resources are here:
http://www.archimatetool.com/developer
Please see How can I contribute code to Archi