Zach, I know that you wanted to keep the post processing time limited but thought that I would throw this in for consideration. As David stated, a good white background makes it easier for the GA’s to remove the backgrounds or to just select the subject. The thought that I want to put out is this. I have noticed that the GA’s often remove the backgrounds and then rebuild the entire image, reason for this; it gives them better control over the final print and choice of back grounds or special effects. Adding shadow, post production, also gives more control on how clean that shadow will print.
CS3 really is great as they listened to the GA’s and added better tools for that application. With a crisp whit background, the “Magic Wand Tool” will quickly select all of that particular color. Granted it also will select some of the brighter sections on the subject but by selecting the “Quick Selection Tool” sized down to your needs and then going into the select folder and chose “Inverse”, you can go back over the area that you want to keep. Go back to the select folder and choose “feather at 2 or 3 and then go to the edit folder and chose copy, then paste. It automatically adds a new layer of just the subject for you. Turn off the background layer and above that layer, and below your new layer, you can ad fill layers or effects layers. Also, you can add one layer that is just a new shadow that you create and control, only the shadow is on it and the rest is transparent. Best part is, no splash or bleed which ends up in a clean commercial print.
It only took me 10 minutes to copy this image, as above, and another 10 minutes to make the background fill layers and shadow layer, including the spot light effect. This is the exact same image that I posted on this thread already, I performed the steps that I wrote out. Granted, if this was for commercial use, I would do a few things different and clean it a bit more but I wanted to share another approach that allows you to reuse backgrounds, change them or just keep cut images for later use.

We all know the degradation effects of drastic down sizing too. so… lol