I also created a plug-in that adds a LWJGL Classpath container for Java projects. This makes it much easier to set up LWJGL projects, just select Add Library -> LWJGL Library -> check optional libs if you want to (lwjgl_util, lwjgl_util_applet, jinput, AppleJavaExtensions?) and the library is added to the Java Build Path, with attached sources (if available) and native file location.
However, I'm unable to build this with ant4eclipse (somewhy it doesn't resolve org.eclipse.jdt.ui) so I'm not sure how this could be added to LWJGL build. Maybe as a binary in SVN?
Was able to build it with Eclipse 3.4.2. The problem was with 3.5.0 and 3.5.1. I think 3.4.2 is a sensible requirement anyway so it makes sense to build with that actually.
There are still a few more details to work on, I'll attach a complete patch when I'm done.