Here's a short bash script that allows you to quickly launch Maya and load your most recent scene file. By using the command mayan and giving it the argument to the project directory you want to open, this script will look into the scene folder of that project and find the most recently saved scene file. It will then launch Maya and automatically open that scene file and set your project.

. /Applications/Autodesk/maya2013/
scene=$(ls -t ~/Documents/3D/maya/projects/$1/scenes/*.ma | head -n 1)
echo "Opening " $scene
maya -file ~/Documents/3D/maya/projects/$1/scenes/$scene -proj ~/Documents/3D/maya/projects/$1

You can save this file as mayan. Then you can make it executable by running

chmod +x mayan

You can then put a copy of your file (or a symlink) in /bin or /usr/bin or /Developer/usr/bin.

To use the command, open up a Terminal session and type

mayan chameleon

Where chameleon is the name of a project directory that you've been working on. You may have to modify the path that points to the project directory of your Maya installation. In my case, my projects are set up in ~/Documents/3D/maya/projects/ but your projects may default to a different location.