Hi everyone. I just happened to find a really nice free Eclipse-based UML modeling tool called Modelio. The free edition can be used for commercial projects also. A 32-bit version for Linux and Windows platform is available.
If you happen to have a 64-bit Ubuntu operating system installed in your computer (which I have, btw :)), just install the .deb package using the following command:
dpkg -i --force-architecture ./modelioFree1.2.1-20101008.i586.deb