I think what Simon is talking about is that Sun, IBM, and Oracle all have their own types of certification tracks.
IBM offers certification for VisualAge for Java, WebSphere, and XML (
http://www-4.ibm.com/software/ad/certify/, and I'll refrain from badmouthing their *products* in this forum), and Oracle offers an "Oracle Certified Java Professional" (
http://otn.oracle.com/training/certification/jdeveloper_ocpds.html ) as well.
I would say definately go for the Sun Certification first because it is vendor independant. I.e., what is tests is your knowledge of the Enterprise Java concepts as a whole. The other certifications are geared towards applying those concepts with or on specific vendors platforms and tools.
If you are working for a company who uses either of those products heavily, it might be worthwhile to pursue.
There are a few others I found to:
BEA:
http://education.bea.com/training/CertificationProgram.jsp. These guys have the lion's share of the app-server market right now.
Silverstream:
www.silverstream.com (they used frames, if you can believe that, so you'll have to go to their search page and use "certification" as the search
word)
Borland: (for their App-Server, which I expected to see start gaining some momentum in the market now, and for JBuilder, which is the most popular
IDE out there, and for their ORB which is top notch)
http://www.inprise.com/services/training/certification/cert_product.html There is also a recent push for a unified certification called JCert,
www.jcert.org Check out the tracks they offer. I don't know much about this but it looks interesting.
Basically, everybody's got a cert program. It generates tremendous revenue for these companies it both instructional and
testing fees.