I've had to revisit this algorithm at work recently in AS2. Which means that I needed to make it as fast as possible. I came up with a nice few tricks to do so as well.

I was so chuffed with myself that I decided to port it to Processing and share it along with how I made the speed boosts.

http://www.robotacid.com/PBeta/fast_astar/index.html

If you can think of any way to make it even faster, I'd love to hear your thoughts. My overhead is at a premium on this project.

Back in the day I started with my own write up of the algorithm, and then TomC came up with one:

http://www.tom-carden.co.uk/p5/a_star_web/applet/index.html

Tom's version was technically more acurrate than mine so I adopted it and then decided to pull out everything that was slowing it down like Java Collections and the endless array sorting and searching. Limiting the search steps is also very important - for bot AI, you don't necessarily need to find the finish node.

So basically - for 3D, we go back to Tom's model of an ArrayList in each Node. Then you'll be constructing a series of waypoints in your map. Bots get the scent, then work through the waypoints to the target.