The answer is that, unfortunately, there is no such thing. emacs-nav offers a file browser similar to a file in ECB, and you can use something like helm to navigate to various materials in your project (e.g. files, tags, imenu entries, etc.). Small utilities, such as projectile , may also be useful for you.
In general, using heavyweight tools like ECB is not Emacs way, and I think that is the reason its development has stalled - fewer Emacs users will use a tool like this with more flexible alternatives.