I started fiddling around with JME3 recently, and finally created a working third person camera with mouselook. I know that’s a Rather Common topic of inquiry 
and though there is already a lot of good information available I figured it couldn’t hurt to add my own example. So I cleaned up the code a bit, made it easily transferable, added some comments and made a page on the wiki about it.
https://wiki.jmonkeyengine.org/legacy/doku.php/jme3:user_examples:ThirdPersonCamera
As mentioned, this is the first thing I’ve made in JME3 that isn’t just copied-and-pasted tutorials, so I might still be doing lots of things in a dumb way. =P I encourage you to point out any such things (and also to let me know if I have used the wiki incorrectly) – but nevertheless, I hope someone may find the example useful. 
Video, made with the astonishingly convenient VideoRecorderAppState (is there any way to embed this in a smaller size? :P)
it’s not that obvious)
Still need to implement the remaining basic camera features like collision or raycasting for walls, etc – but even then, I will leave the basic example intact for posterity. =P Not sure if anyone has tried it yet, but the video has 43 views so I think we can expect to see 43 new games utilizing my exciting technology. 8)