In a custom web map app, when creating your initial view, you usually start with the x/y (latitude/longitude) and an initial zoom level. When creating 3D web map apps that's a bit harder, because you have to worry about the camera tilt and heading too. To make this process easier, I recently shared a little tool …
This was inspired by David Spriggs's js-extent-helper (which I believe was inspired by a Flex version of the similar idea before that).
Please try it out and let me know what you think! The code is posted on Github.