Sainath's Advice on Thursday, May 12, 2011 :
The Agile wave is strong right now - based on the same I would suggest that you target Certified Scrum Master. However, this in itself is not enough - ideally you should be working in actual Agile projects. While the principles are easy to understand, Agile using Scrum is not so easy. The visibility, inspection and adaptation aspects of Agile ensure that you have to answer many uncomfortable questions in the project in double-quick time.
Rather than CAPM you should directly target PMP but at senior developer stage I think it is a little premature. I am saying this as for both the certifications you will need to study the PMBOK (Project Management Body of Knowledge) anyway.