I'm interested in learning UML and would like to choose one of the more popular UML design tools for Linux. Of course everyone has their preferences for what they consider the best but what I'm hoping to find is what is unarguably the most used, most popular among open source dev organizations. (The same way GIT and Mercurial could be said to be two examples of the most widely adopted revision control systems, even if they aren't "the best" in everyone's eyes). It needs to be open source (something I can just install on my Linux system).

Thanks in advance for any direction.