When we were on our honeymoon, our of our vineyard guides told us that bringing a bottle of wine to a party is tricky business in Napa Valley---people really know their wine, they've tried a lot of it, and they probably have quite a collection already (it's the same with barbecue sauce in Kansas City!)...
Instead, he brings a bottle of really good local olive oil---isn't that fabulous? You could also do something like hot sauce, aioli, or preserves.
He also mentioned that some of the infused olive oils are so good that you can just pour them on salads and not even worry about adding anything else for dressing. I've never tried infused olive oils, but this piqued my interest. A good lemon or garlic-infused olive oil would be a nice start. It's worth a stop at Heavenly Olive Oil in Kansas City, or maybe even a weekend afternoon where I make my own.