Many plug-ins are included with the WebDesign download by default. You can find dozens of FREE add-ons for WebDesign on the WebDesign Resources Page.
You can distribute your plug-ins to other users if you would like all WebDesign users to benefit from your work. By signing up to the free resources page above, you can add your Plug-ins and Language Extenions for others to download. User will be able to download, review and get more information about your WebDesign add-on by visiting that resource site.