Agile Delivery Practice revolves around the principle of delivering tangible results in small planned steps usually called as iterations. Agile Testing is not a specialized branch of Quality Assurance and Quality Control but a testing philosophy aligned to the agile delivery model. It requires all which is needed in a traditional testing plus agility :). What's agility? Test engineers are no more expected to sit waiting till the requirements get completed and documented and delivered to test engineers to design and develop test assets. Similarly there is no waiting time for them to prepare test environment, get the build and start testing. Rather, they are running along with all other actors in the system on parallel tracks. Automation is the key to success in Agile environment; without which test assets would become a huge backlog over the period of time and testing would not be "agile" any more.
Agile Testing requires Agile Project Management, Agile Test Management, Agile Defect Management and Agile Report Management. You must be thinking that this person is joking or talking non-sense. But that's correct. In agile environment, everything needs to be agile or you will get confused. Rally is a good tool that provides integrated project management, test management, defect management and report management for test managers who work in Agile Environments. A good testing management office would also have a stack of open source tools integrated smartly to provide the similar capabilities under one roof. Test Management Offices (I have coined this concept similar to Project Management Office or PMO and would be calling it as TMO) without consideration to Agile Testing would suffer a major setback in delivering quality in Agile Projects.
So in short, as developers need to be "agile", tester can not be left "passive". So eventually testers are pseudo developers who are communicating with business analysts, architects, developers and end users. I call it "convergence of development and testing teams to deliver a high quality piece of code in small iterations which makes planning, execution and control phase of project management much easier"