How do you find a good illustrator?

On the CFC LinkedIn Group, Tim Read of 5 Fingers Creative (who will be hosting a breakfast round table for illustrators at this year's CFC) asks this question:

How do find a good Illustrator? What sources do you use when you have a need for quality illustration? How do you decide which one to choose? Are there resources that are better and more effective than others?

Any thoughts or resources to share?