There is another very active 'SOA certification' group on yahoo.
Please join a group ibmsoacert on yahoo. You will find lot of material as well as guide for SOA certification.
I studied the following materials
1)SOA fundamentals in a nutshell
-SOA Governance and Management.pdf - Chap 1,2& 3
-WebSphere Service Registry and Repository Handbook- Chap 1,2&5
4)Some SOA presentation on net
I think your preparation is sufficient. Please go and take the Exam.