I thought it might be helpful for those also interested in taking the OCA examination to describe how I prepared for it.
First of all, I've been in the position of Oracle database administrator for 6 years. Practical experience is much more easy to recall than text from a book.
When I expressed my goal of getting OCA and OCP certifications, my employer was very supportive. At my request, the Oracle 10g OCP Certification All-in-One Exam Guide was ordered. This guide was a good read, although it was written prior to 10gR2, and so some of the contents were already outdated. This book also came with a practice exam that I didn't feel was too bad, although it covered Resource Manager, which was not on the OCA exam, nor in my other study guides.
This January, my employer sent me to the Oracle DBA Workshop, the class recommended for the OCA. This class assumes zero knowledge of Oracle, so the majority of it was review, but there were a few nuggets of gold that I put into practice at work. Just to note, the class is not required for the OCA (unlike the Workshop II class being required for the OCP).
My employer also bought the self-study CDs for this workshop. I went through those over the two weeks prior to the exam.
Obviously these things all cost a bit of money, and my employer thankfully covered the cost of all media and training. Hopefully this helps someone out.