Hi everyone.
I had done few little games using swing or slick2D.
Now, i want tou go deeper with trying to make a first attempt to use directly opengl for rewrite the ui of one of my game (that is built upon swing).
What is the best online tutorial i should follow ?
Thanks in advance for your advices.
There are several decent ones, lots of crappy ones, zero complete ones, and cut that figure by 90% when it comes to covering the topic in Java 
There is one decision you should make though: do you want to learn old-school OpenGL, or modern OpenGL? The first is easier to learn and initially program for, the second takes full advantage of current GPU hardware and is all that will run on most mobile devices.
So, on with the links:
opengl.org code samples and tutorials A big collection of links. If you bookmark one link, it should be this one.
The OpenGL Programming Guide - AKA “The Red Book”. It’s a book, but the first edition is free online. Very much old-school, but goes into concepts, not just code.
NeonHelium Productions (NeHe) - In my opinion, highly overrated, but someone will inevitably mention it. The LWJGL and JOGL ports linked on the page are bit-rotted and don’t run anymore, but substituting slick-util for DevIL will fix some of them (google for “lwjgl-sandbox” to find some working ports [mine] for lwjgl).
Learning Modern 3D Graphics Programming - One of the few tutorials that covers modern OpenGL start to finish. Goes off on some fairly advanced tangents, but the code is easy to follow.
Could the Powers That Be make a sticky in this board that collects the various tutorial links?
Someone updated the port of Nehe tutorials with JOGL 2.0, have a look at JOGL section.
Offtopic:
Just created a bunch of sticky topics in a number of boards. Enjoy!