Related, does anyone know if there are any good tools for learning things about a graph (not necessarily a graphviz graph, but that'd be fine!)? Things like...

Related, does anyone know if there are any good tools for learning things about a graph (not necessarily a graphviz graph, but that'd be fine!)? Things like... take a graph from me and identify all the "islands" that don't connect to each other? Or to find the shortest 'path' from point A to point B in a graph?