Sometimes you want to download NetBeans plugins from outside of NetBeans IDE for example for offline installation. for this purpose :
  1. From menu, go to Tools -> Plugins.
  2. In the last tab (setting), you will see a update centers list (on left side) e.g. "Certified Plugins"
  3. You have to know your desire plugin is located in which update center.
  4. select that update center from list (e.g. Certified Plugins) and then from right side click on the "Edit" button.
  5. from the shown dialogue, copy text in URL text box (do not copy last part of URL, in this case "catalog.xml.gz", only copy the address of  xxx.gz file e.g. "http://updates.netbeans.org/netbeans/updates/7.2/uc/final/certified")
  6. Now you can paste the URL in your browser and find your plugin in folders.

have a nice time.