Superglue! (Not really)

The cracks are caused by irregular watering. The solutions are to avoid alternate flooding and drought conditions. You can apply mulch at the base of the plant to keep the soil evenly moist. Also use a balanced fertilized. The cracks can be caused by too much nitrogen.
The tomatoes are still edible, but they won't keep as long as tomatoes with perfect skins.

Here is a link that might be useful: What's Growing On?

Interesting. This plant was an extra so therefore is planted outside the beds...makes sense that it's watering conditions are less than ideal. I do have mulch at the base, maybe I should add more.

You can find lots of info about radial cracking - what you have - of fruit over on the Growing Tomatoes forum here. Both the causes and prevention tips are discussed in detail there.

Dave

Aili: some varieties are more resistant to cracking, but basically what lgteacher said. Not sure about the whole fertilizing thing, but mine stopped cracking when I started mulching heavily. My watering ritual is about ONE deep long soak per week -- not the every other day soaks I did in the past WITHOUT mulch; and still had cracking. My mulch starts out about 4" thick.

Kevin