I work in a Ubuntu machine
Finding a decent free / open source UML CASE tool for Linux is a bit of nightmare. Some of the Rational tools have 30 day free trials but I found them too restrictive. For example, deployment diagrams in Rational Software Architect are pretty lame, sequence diagrams are hard to customise, and component diagrams are a joke.
In my opinion by far and away the best UML CASE tool is
Sparx Enterprise Architect. However, it's not free and you have to jump through
some hoops to run it in Linux.
Alternatively, why not use
Virtual Box and run a free Windows-based tool inside a guest OS?
SCJP, SCWCD, SCBCD, SCEA 5