Dijkstra's algorithm (to find the shortest path between two nodes) was published in June 1959, so it's about to enjoy its 50th birthday. The great thing about fundamental algorithms is that they can be applied in all kinds of different ways. Dijkstra's algorithm obviously applies to real-world route finding, and I'm sure that inside your car's SatNav system you'll find it lurking there; but networks (data and voice) are much more important than they were back in 1959, and this is a whole new application area.
In multinode data networks, it's still necessary to find the shortest path, in hops or in time, sometimes weighting hops in terms of real-life cost in order to give a "least-cost" route. Routing IP packets depends on finding the best routes from "A" to "B" without looping. In voice networks, a more subtle form of "shortest" is needed: that is, the path with the lowest latency. Latency is much more of a problem today than it was in the past because the 'nodes' in VoIP networks are often processing elements that add delay as part of the transformation they perform, e.g. transcoding, echo cancellation, tone detection and squelching.
So Happy Birthday, Dijkstra's algorithm; may you continue to find new applications.