No one likes to be lost in a sea of unknown words. With GNOME Word of the Day Applet, your vocabulary will evince perennial growth. It's a must when preparing for the SAT or GRE tests and for improving both reading comprehension and writing precision.
GNOME Word of the Day sits in your panel area as a word or an icon.

You can retrieve words from many online sources, and have them cycled through every few hours.
Download the latest 0.2 tarball or deb.
sudo dpkg -i gnomewotdapplet_0.2-1_all.deb
tar -xvzf gnomewotdapplet-0.2.tar.gz
cd gnomewotdapplet-0.2
./configure --prefix=/usr
make
sudo make install
GNOME Word of the Day is a .NET application written on top of Mono targetted for the GNOME desktop, released under the MIT license. It's written by Phil Crosby and Mike Quinn.
Developers: instructions for checking out the source.