I'm looking for software (preferably free!) to use to help me draw good-looking conceptual diagrams for publication. I typically default to Word or PowerPoint but their drawing tools don't offer the kind of functionality and professional look I've seen in some publications.
By 'conceptual diagram' I'm referring to something between a mind map and flow chart. Think about the kinds of diagrams people use to explain the structure of a thesis, or to model an information flow, or to present a conceptual framework...