I got your pm, replying here.
I was wondering if there was a kit, a parts list, a how too, a walkthrough, a tutorial for dummies (ok you get the picture) on how I could do this?
DNA dan's thread is the closest to a tutorial on friction wheel drive rotation. I assume one of Chopper's links above is to that, otherwise search DNA dan.
Since a monitor is rectangle, how do they get the bezel to spin too?
I used a fixed bezel with a square opening- the monitor rotates behind it.
What options are available to make the screen rotate? I would prefer the easiest method of course
Friction drive wheel with usb control is in my opinion the easiest way. there are complications that can be added - parallel port drive instead of usb, h bridge control instead of motor controllers, different drive schemes including fully geared/stepper motor (ond style) chain/sprocket drive, edge of wheel drive, rope drive, pull it out and put it back in sideways drive (lechuck). There are different means of rotation - lazy susan (DNA dan) axel and pillow block (Ond, Khalid74) edge mounted with a bike rim, etc.
you have to match your rotation method to the size and weight of your display. small LCD is easier than large CRT.
Whats the cost? is it cheaper to make a vertical only cabinet? space is an issue in my home.. so the idea sounds cool.
The friction wheel method I used added about $100 in parts from Pololu and the hardware store.
With mame, can it auto rotate the screen when a player selects a vertical game? or would I have to press a key?
yes, although you need mala as the FE to send rotation commands. if you use hyper spin or another fe you may need to do autohotkey scripts to call for rotation. Mame can handle giving the FE the information about whether the game is horizontal/vertical. it's in mame.xml.