The next java cert after SCJP really depends on your career and interests. SCJD focus on Swing/desktop, SCWCD is web (servlets/JSP), SCBCD is
EJB. Or you may consider SCMAD (J2ME) or the architect cert (
SCEA).
Most people I know tend to go for the web cert cos most people are doing web development. But honestly, I personally think SCJD or SCBCD is more valuable. SCJD tests your OOAD skills. SCBCD is what Java EE people called the internals of the Java EE platform. Correct me if I'm wrong on the that.