The MazeSolver.zip file at the Rule Table Repository has been updated to include an extended version of Adam Goucher's MazeSolver rule called MazeSolver2. The new rule uses the Moore neighborhood to allow diagonal filling and backtracking (and thus finds a shorter path through a maze).
If using Golly 2.1 or later you can download the new zip file from Golly. Click on Help > Online Archives > Rule Table Repository, then download MazeSolver.zip using the link near the bottom of the page. Have fun!
EDIT: I forgot to mention that the order of states in MazeSolver.table in the new zip has been changed so that MazeSolver and MazeSolver2 can share the same starting patterns. If you have any patterns saved using the old MazeSolver rule you'll need to edit the start and finish cells.