FreeMind is not available for Chrome OS but there are a few alternatives with similar functionality. The best Chrome OS alternative is TiddlyMap, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 100 alternatives to FreeMind and four of them are available for Chrome OS so hopefully you can find a suitable replacement. Other interesting Chrome OS alternatives to FreeMind are Mindmup (Freemium), ProcessOn (Free) and Goalton.com (Freemium).
TiddlyMap is a TiddlyWiki plugin that turns your favourite personal note taking software in a wiki-concept-map hybrid! Yes, you will be able to do both: drawing maps and putting down knowledge in a wiki way.