I've never been sold on the Iraq-Al Queda connection, but here's an interesting article nonetheless.

I do think it was reasonable to look into Iraq - here's an interesting piece on the 1993 World Trade Center bombing. (Sorry, it's real long)

Bottom line with 1993 - we were lucky. The cynide in the bomb burned in the explosion and Yousef was unable to get as many explosives as he wanted and therefore only six people were killed. He came into the US with an Iraqi passport and he stayed with Iraqi's when he lived here. One of the co-conspirators arrested with him had placed 26 calls to Baghdad, presumably to an uncle there. I dunno, there's some evidence to point to the 1993 World Trade Center being connected to Saddam, especially in light of the plot to kill Bush I in Kuwait post-Gulf war. This lingering evidence is enough for me to think looking into an Iraq connection to 9/11. I don't think it was unreasonable to do so.

That being said, I don't think we've established a clear connection and don't think that is the reason we went to Iraq. But what is clear to me is that getting rid of Saddam will help the region and help us because it'll give us one less major thug to worry about.