I go to know agile as a developer, after I learned that “my smart/lazy” way of testing a screensaver was done before and was called unit testing. And I learned about extreme programming. At that moment both Scrum clearly said you needed technical excellence, and I remember talking about scrum in 2005/6 where they said, We don’t want to define what is technical excellence as XP does this already.
Yet it seems sometimes that the agile world has forgotten about technical excellence.
In this list I want to link you to resources that teach you technical excellence.
(resources being book, video’s, blogs)