Someone else could maybe post links and commentary for OMONDO & Poseidon/Argo UML. Here's some links to Dia for Linux & Windows. Note it ships with Redhat 9 desktop installs & other Linux distros. It has a UML Shape Library ready to roll. It's not a dedicated UML tool, which can be a benefit if you need some way to express yourself graphically for other purposes (for free). However it may lack the features you want for 'round trip' UML <-> Class modelling. Dia Home Page: http://www.lysator.liu.se/~alla/dia/ Dia Windows Installer: http://dia-installer.sourceforge.net/ On sourceforge.net, you can also find a number of scripts / add ons that enable Dia to produce things from it's drawing files (like SQL) & others that produce Dia files from things (like DB connections).