This is basically an Objective-C port of Mat Buckland's C++ graph classes, as described in his excellent book Programming Game AI by Example. More info on Mat Buckland's book and sample C++ files are available at http://www.wordware.com/ai
OGraph lets you model directed and undirected graphs with nodes and edges, and perform a variety of search algorithms on them, including BFS, DFS, Dijkstra, and A* (AStar).
In a nutshell:
// make a graph
SparseGraph *graph = [[SparseGraph alloc] init];
// add some nodes
[graph addNodeWithIndex:0];
[graph addNodeWithIndex:1];
[graph addNodeWithIndex:2];
// add some edges
[graph addEdgeFrom:0 to:1];
[graph addEdgeFrom:1 to:2];
// search it using a search class
GraphSearchDFS *dfs = [[GraphSearchDFS alloc] initWithGraph:graph sourceNodeIndex:0 targetNodeIndex:2];
NSArray *pathOfNodeIndexes = [dfs getPathToTarget];
...
Check out the unit tests for more examples.