As a matter of opinion, it's not too far a leap of faith to go from the documented links between Saddam's regime and its support of AQ operatives and the specific operation that resulted in the 9/11 attacks.

The question seems to me to be asking about belief or opinion ("do you think"), as opposed to certain knowledge.

"Do you think Saddam Hussein’s regime in Iraq was directly involved in planning, financing, or carrying out the terrorist attacks of September 11th, 2001?"

Sadly, the 9/11 Commission came to its conclusions, held its hearings, and published its report (in that order, btw) without benefit of information gained through exploitation of captured Iraqi government documents.

So the 9/11 Commission's report must necessarily be considered incomplete (at best).

Did you happen to notice the high-ranking AQ leader who, when wounded in the U.S.-led invasion of Afghanistan, fled to Iraq where he received sanctuary and aid?

Do you recall the location and date of Abu Nidal's death? Okay, not AQ but the GWOT has never been limited to AQ (nor should it be, for reasons which should be self-evident).

As for the CIA, the only connections I see from them to the 9/11 attack was their part in the systemic inability to detect/deter/neutralize the 9/11 attackers. Never attribute to malice that which can be explained by stupidity.

So to answer your question, I think those who believe the CIA was responsible for the 9/11 attack have been grossly misserved by those who publish the newspapers they read and the television news they see and hear. It's arguably not their fault they are so mis-informed. Which means they're merely ignorant, not stupid. Woe betide their news organs when they finally learn how poorly they are informed.

And as regards the some of the responsibility for that systemic inability, see 9/11 Commission member Jamie Gorelick.

I would also refer you to Pres. Bush's Sept. 20, 2001 address: http://www.whitehouse.gov/news/releases/2001/09/20010920-8.html

Especially these parts:

"Who attacked our country? The evidence we have gathered all points to a collection of loosely affiliated terrorist organizations known as al Qaeda."

"This group and its leader -- a person named Osama bin Laden -- are linked to many other organizations in different countries, including the Egyptian Islamic Jihad and the Islamic Movement of Uzbekistan. There are thousands of these terrorists in more than 60 countries. They are recruited from their own nations and neighborhoods and brought to camps in places like Afghanistan, where they are trained in the tactics of terror. They are sent back to their homes or sent to hide in countries around the world to plot evil and destruction."

&

"Our war on terror begins with al Qaeda, but it does not end there. It will not end until every terrorist group of global reach has been found, stopped and defeated."

As for WMD, quite a few WMD were found in Iraq, but for some reason that doesn't get a lot of press. Apparently people in the media get to re-define was constitutes WMD to fit their agenda. On one day, White Phosphorus grenades seem to be qualify and on another binary nerve agent shells do not.

Please read the Iraq War Resolution (http://hnn.us/articles/1282.html) for the 23 articles which the U.S. Congress thought sufficient causus belli for the U.S. to invade Iraq. Only some of them have to do with WMD.

I would concede that the WMD rationale was over-emphasized in drumming up popular and international support for the invasion, but it was never the sole justification.