pd:

I do not believe any ITX boards have AGP slot. THe board I have has a built in AGP 2d/3d card. I know its not as good as the GForce or the ATI since I benched it on 3DMark. But it does a good enough job on DVD since it has DVD hardware chips on board for motion compensation. and the CPU isnt chugging along during DVD playback.
If you want and ATX slot then for small form factor the Micro-ATX board do have the AGP slot. Its a little bigger than the ITX. But I believe some of those Shuttle box do have proprietary boards built by MSI motherboards and they have AGP slots but in a weird form factor around the size of ITX.