VisualGC is now available as a NetBeans Module.
VisualGC is part of a broader set of tools to monitor the JVM called jvmstat. These tools have allowed users to have JConsole-like tools to get thread dumps/stack traces, detailed memory usage, time spent in GC/ClassLoading/ClassCompile, startup options, and more all since 1.4.1 JVMs. With Java 1.5.0 available, of all the jvmstat tools, visualgc is the only one that does not have an equivalent in the new monitoring, management and troubleshooting tools.
Whether you want to learn about the internals of the JVM (eden, survivor spaces, …) or actually solve some problem, you should give VisualGC a try (with or without NetBeans).