Im planning on putting halogen lights (regular 120V) on the top of the poster boxes, but I absolutely want them to be dimmable with a standard Lutron Dimmer.

Is this possible?

If not, does anyone know of a small (3" or less) can light that will use a standard incandescent bulb? It needs to be ablte to rotate at an angle (eyeball type).

Thanks for any suggestions, Im struggling with this one!

Yes they can. I use 12 120V halogen spots on track lighting for my theater room on one of those Lutron remote dimmers found at home depot etc.

Yep - I have some 120v halogen track lights on Lutron dimmers - works fine.