Iraq-Al Qaida connections are well-documented in Stephen Hayes' or Richard Miniter's books. It's obvious that Saddam and Bin laden were linked, both wanted to destroy America.
Iraq is also strongly suspected to be behind 9/11 as supportive regime. Terrorists in Salman Pack were trained to hijack planes and paid by Saddam. The Atta-Iraqi ambassador meeting in Tcheckya has been attacked by the 9/11 commission, but they had no definitive answer. It's clear now that the 9/11 commission spent more time clearing Clinton's disastrous record on the War on terrorism than looking for Saddam-Bin Laden links.
Zarkawi's group on northen Iraq was also linked with Saddam, who gave money to them. Al Qaida's operative in Afghanistan moved in Iraq in 2002.