There are many slideshow boxes out there I'll just share my google on it.
https://www.google.com/#q=raspberry+pi+slideshow
https://www.google.com/#q=raspberry+pi+digital+signage+solutions
Before the raspberry we would use one netbook per sign.
The people in my department and I are stumped about a good program that will manage our multiple monitors. All we really want to do is have a slideshow run. The problem it seems is that most the solutions we find are cumbersome or only manage a few monitors. We have 5 vertical monitors. Ideally, we'd run a slide show. Each of the 5 monitors would run a group of slides and then switch to the next group of five. Does anyone know of software that will meat our needs. Obviously googling has gotten us no where. In the past we had used QLab but we really don't want something as complicated as that.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic