Which websphere certification is suitable and valuable?

I am a java programmer with SCJP and SCJD certification. I attempt to go deep in J2EE. Some pioneers here suggest that I should go get IBM websphere certification instead of BEA weblogic. Since there are many websphere certifications that confuse me, Could you please tell me what kind of IBM websphere certification is suitable for me? Importantly, what kind of websphere certification is valuable for job market in the States? Thanks a lots!

http://www-1.ibm.com/certify/tests/obj158.shtml

For a list of all WebSphere certifications, look here: http://www-1.ibm.com/certify/certs/ws_index.shtml
Since you have already achieved Level I certification (SCJP), the next steps for you are:
1) Level II certification - IBM Certified Solution Developer: http://www-1.ibm.com/certify/certs/adsdwsap43.shtml
2) Level III certification - IBM Certified Enterprise Developer: http://www-1.ibm.com/certify/certs/adedserv40.shtml
Unless you are interested in Portal Server, Commerce Server, or MQ, you should focus on achieving the above listed certifications for J2EE.
IBM is currently offering free vouchers for certification for developers that pass the the pre-assessment (ICE) exams. For more information, look here: http://www-1.ibm.com/certify/news/20021108.shtml
For general certification information, including job roles, look here: http://www.jcert.org/