If I were Saddam, I would pull back all of my Republican Guards divisions into Baghdad, have a special unit dressed in US uniforms commiting atrocities against my people, and spread the photographs in Baghdad, so that people of Baghdad will also fight against the invaders.
When Americans will nearing Baghdad I would destroy the dam on Euphrates (or was it Tigris?) to slow down the US advance, I would also set fire to major oil wells.
Before my communications are cut off, I would appeal to Arab nations to send mujahedeen to Iraq to fight the infidels. I would also transfer some of my money to Al-Qaida, Hamas, Hezbollah and other terrorist organisations. Also before Baghad is fully surrounded I would try to get some WMD out of Iraq, so that operatives of the above mentioned organisations can use them "appropriately".
If everything worked to plan, US military should now be involved in a bloody battle in Baghdad, with Al-Jazeera showing exclusive footage of US military and Iraqi civilian casualties. While still in Baghdad, I would constantly keep moving from one bunker to another. When things get really desperate I would shave off my moustache, dye my hair, change my clothes and escape from Baghdad. Before that however I would try to fire off all my remaining WMD stocks (hoping that something hits Israel).
As I escape together with a flow of refugees, hopefully Israel would launch some retaliatory strike against what's left of Baghdad, inflaming the whole of the Middle East.
Now my mission is over. Middle East is in flames, and I'm still alive. While on the run, I would be thinking about how to topple the newly-installed US puppet government.
(Note: this is a nightmare scenario, but Saddam is quite clever in his own way, so it is possible that he will try to achieve something similar)