I'm a big fan of graphic novels that use their imagery to tell stories that need to be told. That's not to say that pure fantasy GN aren't interesting, but sometimes, when people don't dig things like novels, paintings or art movies, or even history books and the news, GN are the perfect portal to reach them.
I've talked before about Barefoot Gen, which deals with Hiroshima from a Japanese perpective. There's also Art Spiegelman's Maus, which talks about the Holocaust (Spiegelman also drew a graphic novel about 9/11, called In the Shadow of No Towers). And there's also Marjane Satrapi's fabulous GNs about being a woman in Iran during the Iranian Revolution and beyond. I have her Chicken and Plums, and her Persepolis is about to be released as a movie.
That's just a short list of the most obvious political graphic novels. If you're interested, get thee down to the local (good) comic shop and ask what else they have. Or share in the comments if you have a personal favorite.
Today, whilst doing my early-morning blogsphere cruise, I followed a Hoyden link to a very immediate graphic response to the Chinese earthquakes. Go there, but with a box of tissues. These excellent drawings do more to bring the suffering home than any number of news stories. They evoke compassion and even, in some cases, raise a smile. Highly recommended, especially for 'whatever' teenagers.