<a href="http://www.cdrinfo.com/Sections/News/Details.asp?RelatedID=2351" target="_blank">Sanyo CRD-DV1</a>
4X DVD-R
2X DVD-RW
For comparison, the SuperDrive does 2X DVD-R and 1X DVD-RW.
Also the Sanyo is supposed to be able to burn 1.3 GB to a CD-R/W. Whether this is useful is another question.