I highly recommend this site by Christophe Riccio (you probably want to subscribe to this RSS feed).
The OpenGL Samples Pack contains a large number of modern OpenGL samples, covering almost every feature introduced from GL 2.1 to GL 4.1. Even though the samples are written in C++, everything is perfectly clear and easily portable to LWJGL/JOGL. All the samples are written in a forward-compatible way (no deprecated stuff) and are frequently updated.
Christophe has also written an extensive test suite for modern OpenGL drivers and posts his findings every month or so, here. Very useful if you plan on using OpenGL’s cutting edge features and want to avoid unnecessary headaches.