[sourpoi]

Of the free GUI tools, BOUML (the old, open v4.21 in Fedora 18) had the best combination of available UML components and editing flow. BOUML was restricted/automated enough to give me the impression that I was describing relations more I was drawing them.

However, at the end of the rainbow I found PlantUML. PlantUML renders nice graphs using a GraphViz/Dot-like language and affords all the benefits of being plain text - revisions are intelligible, syntax is highlightable, and edits flow at the speed of Vim.

http://plantuml.sourceforge.net/