Name some Web sites that make extensive use of Servlets.

jGuru makes use of both Servlets and JSP, naturally.

Sun has a small list of "Servlets in the Real World" at http://java.sun.com/products/servlet/industry.html#real.

See also this question in the JSP FAQ for a list of JSP-using sites.

Please submit other sites you know of as feedback to this question.