
Pencil Project
Pencil is a standalone app or Firefox extension that lets you create diagrams or UI mockups. It doesn't have collaboration/multi-user features.
PathVisio is a free open-source pathway analysis and drawing software that allows drawing, editing and analysing biological pathways.
PathVisio is a free opensource pathway analysis and drawing software that allows drawing, editing and analysing biological pathways. It provides a basic set of features for pathway drawing, analysis and visualization. Additional features as plugins.