I am really interested in deferred rendering. Does someone have any experience with it or at least any ideas of how it is supposed to work or any good links? 
What links and other resources do you have already? (I only just skim-read a couple articles myself). If you were to do a project of this sort for jME 3.0 I'd say we'd need to see some substantial preliminary work in that area to support it. The jME 3.0 core has little room for 'first-attempts'.
When choosing the lucky few applicants, we'll definitely be taking initiative and independence into great account. Of course, reaching out also plays an important part ;D It's all about that middle road…
There's a lot of resources on the internet about deferred rendering, a tutorial came out on GDNet recently:
http://www.gamedev.net/reference/programming/features/defRender/
jME3 is able to support deferred rendering by creating proper techniques for gbuffer and lightpass in the appropriate materials, it will also require using SceneProcessor. The only thing jME3 is missing is MRT (if I remember correctly).
And erlend_sh is right, jME3 does have little room for 'first-attempts' 
as we are going into alpha soon. It will be best if you're well acquainted with jME3 and the thing you're going to implement.
I read some articles some time ago, but never really tried programming such a thing. I played with shaders a little, and I have lots of experience with JME2 (my project uses JME2 since JME3 is not stable atm), also I have some experience in LWJGL, since I used it for one of my seminars at faculty. The article you provided is really informative, and I will try to read it more closely in the following days. Anyway, I am not sure yet that I will apply for GSoC, since I will have my last exams in June and then take a week off to visit England. But if I do, I would really like to try and implement deferred rendering. Anyway, lets wait till 18th March to see if Google even accepted JME (sadly they are mainly interested in C and Python as I heard)…