How to make a shaped gradient transparency in photoshop cs5

I am trying to blend photos into a colored background, ridding them of the their edges. I have tried many techniques including the quick mask option -> filter -> artistic -> inverse and cut out middle etc. In essence all I'm trying to do is:

Is create a gradient out of the photos, that starts from the middle of the photo to the end, and be able to control the amount of the transparencies as well as the the size of the gradient all in CS5.