I've always been intrigued by Map Routing, but I've never found any good introductory (or even advanced!) level tutorials on it. Does anybody have any pointers, hints, etc?
Update: I'm primarily looking for pointers as to how a map system is implemented (data structures, algorithms, etc).
By Map Routing, you mean finding the shortest path along a street network?
Dijkstra shortest-path algorithm is the best known. Wikipedia has not a bad intro: http://en.wikipedia.org/wiki/Dijkstra%27s_algorithm
There's a Java applet here where you can see it in action: http://www.dgp.toronto.edu/people/JamesStewart/270/9798s/Laffra/DijkstraApplet.html and Google you lead you to source code in just about any language.
Any real implementation for generating driving routes will include quite a bit of data on the street network that describes the costs associate with traversing links and nodes—road network hierarchy, average speed, intersection priority, traffic signal linking, banned turns etc.
A* is actually far closer to production mapping algorithms. It requires quite a bit less exploration compared to Dijikstra's original algorithm.