Having recently discovered this group and having a long association with Marathon, I'd like to give something back to the community.
I'm an audio engineer in Chicago http://crc55.com and I'm also an audio instructor at Columbia College http://directory.colum.edu/departments/19.
I have access to over 700,000 licensed sound effects and dozens of students who would love to create original sound design for your projects. Free of charge.
All I ask is that your project is fairly developed and that you give credit to my studio and any students who participate.
Contact me at mcoyle@ChicagoRecording.com or mcoyle@Colum.edu.