There's an A* example in the BlitzMax sample folder, and an A* example on the BlitWiki.
[a http://www.blitzwiki.org/index.php/Category:AStar_Pathfinding_%28Module%29]Astar pathfinding module[/a]
[a http://www.blitzwiki.org/index.php/Category:AStar_Pathfinding_%28Module%29]Astar pathfinding module[/a]