CardBoard allows teams to collaborate online and build whatever they can imagine. It is designed to be simple to use so you don't need to go through a ton of training. Get your whiteboard started quickly by using one of our built in templates. Hold your next retrospective or agile planning meeting with CardBoard. Try now for free => https://cardboardit.com
Xmind - Xmind is a brainstorming and mind mapping application.
openDesktop.org - The website openDesktop.
FeatureMap - FeatureMap story mapping, simple and effective realtime collaboration and collective intelligence tool.
SourceForge - The Complete Open-Source and Business Software Platform.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Freecode - Freecode (formerly known as Freshmeat) is one of the legit open source development platforms that will be the key for developers and programmers to have a streamlined process via having enhanced collaboration and coding leverages.