I would expect your local paper would have that information as the competitions come up. My paper runs a weekly article about upcoming cooking classes and events in the area.
Similarly, ask some of the vendors. Sur la Table probably sponsors an event or two. A barbecue restaurant could tell you about barbecue competitions and so forth.
And check out the websites of various specialties. IDOS > Home
would have info about any dutch oven cookoffs for example.
You might also try writing the person at your local paper who covers the food beat in general, not just the restaurant reviewer. They should have a pretty good calendar of the events as they'll probably be covering them.