Juan Nunez-Iglesias, a fellow core-developer of scikit-image, and I gave a scikit-image tutorial at SciPy 2014! I gave the first 2 hours (minus a quick intro), and Juan gave the second 2 hours. Surprisingly, this was the first tutorial at the (U.S.) SciPy conference (Emmanuelle Gouillart gave a tutorial at EuroSciPy 2013).
Anyway, if anyone happens to have 4 hours to kill, here are links to the videos:
But, even if don't want to watch these videos, the accompanying notebooks are worth a look: notebooks on github. Currently, the scikit-image website doesn't have any introductory tutorial docs, so this is probably the most complete source for introductory material. I'd like to integrate these notebooks as a user guide on the website, but that may take a bit of time.