When I worked at CSUMB, myself and another employee took the RSS feed from an application I managed which was trying to be the campus-wide calendar and developed a Flash page which displayed all of the items from the RSS feed on a web page. Once we had that we could display that page anywhere. Much simpler as compared to free or purchased Digital Signage software.
This is the project which inspired my RSS Slideshow project. Having that, I was very excited to find this Instructable titled Digital Notice Board for Schools which goes through the steps of setting up a monitor to always display a web page, full screen. But the part that I was most excited about is the fact that the builder included instructions on how to incorporate a motion sensor into the system using a USB mouse, very cool.