I don’t have too much to add as others have already posted on the loss of this important thinker and Rosh Yeshiva who has had a tremendous effect on Modern Orthodoxy, both here and in Israel. See the following blogs for more information:
Baruch Dayan HaEmet: Rabbi Yehuda Amital – Failed Messiah posts an article published by Ynet.
Honestly Frum – contains a link to an important article written by Dr. Alan Brill which reviews the writings of and about Rav Amital for an English speaking audience. He posts from the opening of that article.
To get some insight into his thinking, see one of his email series’ published on VBM, Jewish Values in A Changing World.