See the Scrum Alliance page that describes the Certified Scrum Developer program.
Also see Jeff Hoover's Quest page for this course.
* UPDATE - Sept. 1, 2010:
The mechanism for applying for the Scrum Alliance Scrum Developer Certification is now available.
The Agile Developer Skills course satisfies the Basic Developer Skills portion of the certification requirement.
If you also hold a Certified ScrumMaster (CSM) certification you may now apply for the CSD.
The application can be found at: