This question belongs in fact in the IDE forum. Have patience and a moderator will move it sooner or later.
I have never heard of an ADF plugin. What exactly do you mean with it? What exactly do you expect of it? Try the Eclipse Plugin Central website. If nothing is found there, then the chance is big that it simply don't exist. At any way, I also really don't see why you need a plugin to be able to use ADF. All you need is basically to download the ADF JAR file(s), place it in the classpath, declare the ADF taglib in the JSP and that's all!