Mask photographs and create a collage

Need to mask maybe 100 photos from a party then arrange them for a collage srgb 7200 pixels x 5400 pixels. Need to be able to start immediately and be able to communicate via skype, google talk, or windows messenger. The masking that is required does not have to be very precise, a quick feather edged mask will do. The images will be resized smaller to make up the collage.