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One of the key values of the NetBeans IDE is extensibility, and of course plenty of extensions are available, from debuggers and profilers, to UML tools, to at least one Minesweeper game. A number of online resources list and allow you to download modules for NetBeans. The primary ones are as follows:
There are a number of open source modules for NetBeans that are not currently in the standard distribution. Some are simply too esoteric to be of interest to most users; others are useful, but not currently maintained; others are alpha, beta or experimental modules that may at some point end up in the main IDE distribution.