In a video presentation (via InfoQ), Scott Ambler talks to a testing user group (TASSQ in Toronto, Jan 2006). He explains agile methods, in particular Extreme Programming, and talks about the the role of testing and QA in agile projects.
He recommends that testers and QA people become generalising specialists because, in an agile team, they're not going to spend all their time testing. They need to collaborate intensely with everyone in the team and need to be flexible and communicative. They can specialise in testing but they also need to be able to do some programming, some data modelling, get involved with build and deployment activities, understand the domain and work closely with the Product Owner to identify and evolve user stories (capturing their details in acceptance tests), and pick up other skills as they're needed.
Elisabeth Hendrickson is a tester who has become a generalising specialist through her experiences working in agile teams. Watch her video about agile testing delivered at Google.