Peter Mead has a short but helpful article about being a spring or well of your own sermon illustrations. He gives four categories of illustrations, but I would strongly suggest that you click over to his site and read his explanation of each one.
Here is a simplified list of sources for illustrations, and the order is deliberate:
1. From the experience of both speaker and listener.
2. From the experience of the listener, but learned by you.
3. From your experience, but learned by the listener.
4. From neither your experience, nor theirs.
Check out what Peter says about each of these at: 45,000 Great Preaching Illustrations « Biblical Preaching