Roger L. Simon has several links, and writes that Haaretz is probably the best place to keep up to date on Sharon's condition.

The Haaretz lead story sounds particularly grim:

Prime Minister Ariel Sharon suffered a "significant" stroke with "massive bleeding" in his brain late Wednesday night, according to a Hadassah University Hospital official, and Sharon's authority has been transferred to Deputy Prime Minister Ehud Olmert.

In a brief statement outside the Jerusalem hospital, Dr. Shlomo Mor-Yosef said Sharon had suffered "a significant stroke," adding that he was "under anesthetic and receiving breathing assistance."

A few minutes later, Mor-Yosef emerged to say that initial tests showed Sharon had suffered a cerebral hemorrhage, or bleeding inside his brain. Addressing reporters in English, Mor-Yosef said Sharon had "massive bleeding and was being transferred to an operating theater."

Channel 2 TV said Sharon was suffering from paralysis in his lower body. Analysts on local TV stations said his life could be in danger.

Update: Omri Ceren is living blogging the news on Sharon.

Another Update: "Type and you shall receive":

...a radical Palestinian leader in Damascus, the Syrian capital, called Sharon's health crisis a gift from God.

"We say it frankly that God is great and is able to exact revenge on this butcher. ... We thank God for this gift he presented to us on this new year," Ahmed Jibril, leader of the Syrian-backed faction Popular Front for the Liberation of Palestine-General Command, a small radical group, told the Associated Press.