I mentioned the Strobist and I reiterate it again. The site is one of the best resource on the web for flash photographers.
This was shot on ambient light with two flashes. They were half a foot to one foot away, crossing each other and about 45 degrees above the mug. In other words they were pretty close to the subject. Notice how the cross lights revealed the interesting texture and how the shadow depth of field of the lights contributed to a relatively dark background.
I love this shot and enjoyed the creative process.