I thought this was a great idea for a restaurant ad that’s only really possible because of the dynamic properties of digital signage:

Larger image (from electric-avenue.com)
Share on Digital Signage CornerTags: advertising, lcd, ooh, out of home, transit ads

[...] but other times, the content prevails leading to some great ads like the Teehan+Lax Telus ad, this Marks & Spencer’s campaign on London Underground digital LCD screens, or the above-mentioned Amnesty International [...]