I am in charge of publicity for the Creativity & Cognition Conference. As a member conference of the ACM, we got a free full-page advertisement in the ACM magazine. I gave the design of it a go. I'm pretty happy with it.
The background image, which appears to be done with ink and a brush, was actually done using one of my favorite iPad and iPhone applications, Zen Brush.
It mimics East Asian brush painting. I can do it from my sofa, and there's no cleanup.
I've practiced calligraphy and brush painting for a long time, but it still amazes me that I was able to make the design above in about one minute on my iPhone. Then I emailed the image to myself and made this advertisement by adding text, which was finished in Adobe Illustrator.
Here is the background alone: