Thinking has, many a time, made me sad, darling; but doing never did in all my life. . . . My precept is, do something, my sister, do good if you can; but at any rate, do something.
The best source for finding an agent is called Literary Agents of North America. It's a complete list of agents, not only by name and address, but by type of book they represent and by what their submission criteria are.