I just can't find a decent (and free) one. What can I use?
Did you ever try Umbrello? Given it is based on KDE, however is the best tool I have encountered if you do not want to go the java route. Umbrello is in the Ubuntu repository.
If you are ok with java, ArgoUML is a quite good tool, or you can see what plugins are available for eclipse.
sudo apt-get install dia
Umlet is a great, free, open-source UML tool with a simple user interface:
- you can draw UML diagrams fast,
- produce sequence and activity diagrams
- export diagrams to eps, pdf, jpg, svg, and clipboard
- share diagrams using Eclipse
- create new, custom UML elements
and UMLet runs stand-alone or as Eclipse plug-in on Windows, OS X and Linux.
(Also, check out its sister tool PLOTlet to create chart grids.)
Its among the best and my personal favorite !
I use Papyrus, a suite developed by the Commissariat à l'Énergie Atomique in France that is today available as a plug-in to Eclipse. It is the most advanced open source modelling tool I am aware of and supports UML2 almost entirely. Broad description:
Papyrus is aiming at providing an integrated and user-consumable environment for editing any kind of EMF model and particularly supporting UML and related modeling languages such as SysML and MARTE. Papyrus provides diagram editors for EMF-based modeling languages amongst them UML 2 and SysML and the glue required for integrating these editors (GMF-based or not) with other MBD and MDSD tools.
Most importantly, Papyrus supports Model-Driven Development (MDD), being a pretty able tool to develop Domain Specific Languages. On this regard, Papyrus seems to be the only open source tool supporting the Model-Driven Architecture (MDA) pattern issued by the OMG. With a code generator such as Acceleo you end up with a full MDD stack - from which you may even create your own DSL plug-ins.
After a longe search in desktop apps I decided to go web, now I'm using Cacoo, which allow not only uml drawing but a lot of different drawing (like network topography, general stuff, etc). It's free and allow to share with friends and concurrently editing.
I like yEd. It is not open-source but it is freeware and cross-platform, handling many types of diagrams and also UML.
Gaphor is decent. It has some limitations and bugs, but it is the least annoying of UML editors out there. However, as Dia, it cannot generate code, I am just listing it in case you ever need a straight UML diagram creation tool.
So far Astah* is the best UML tool I've ever used. In my opinion, the drawing experience is better because it can automatically align or anchor the graphical elements in a smart enough way.
They used to provide a free community version but unfortunately they have stopped that support since 2018/09/26.
However, its UML Editor provides a free version if you are a student.