Freeplane - Freeplane is a powerful and free software for building mind maps.
Visual Understanding Environment - Visual Understanding Environment (VUE) is a mind-mapping and concept-mapping tool.
Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.
ShuffleInspire - ShuffleInspire seeks to provide inspiration and boost production to builders and makers in the online community.
OmniOutliner - OmniOutliner is a writing app for collecting information, outlining ideas, adding structure to any sort of writing.
Aibase - Creative Data Manager