I've been considering Photoshop for a while and now and just recently decided to make the leap. Being a little clueless on how to actually use it, I'm consulting a variety of things from online tutorials to the "Dummies" series to help me along the path to enlightenment.
Anyway, one of the things I've always been interested in learning is how to remove those pesky grey casts from photos shot against a white background.
I found this tutorial, which shows you a super-easy way to do it. I applied the technique to one of my favourite old photos and you can see the results below.

Actually, this can probably be done in any photo editing program that allows you access to "Levels" (I think the program that came with my SLR did).
However, in the photo immediately above (as you'll probably notice) the colours have been somewhat degraded by the whitening process and it's here that Photoshop allows you to go one step further in taking them back to a more natural hue. As I discovered in my Dummies book, after adjusting "Levels" as per the tutorial you then choose "Edit, Fade Levels" and then in the pop up box change the mode from "Normal" to "Luminosity".
Sounds a little technical, but hey, I'm going with the flow here and it does look somewhat better as you'll see in the next example (note, especially, the more natural look of the red dots on the fabric....)

Also, whilst this can lessen grey casts it doesn't necessarily get rid of them entirely. To do that you'd need to remove the background completely. That would require a different Photoshop process which is a little more involved and which I'm yet to try.
Here is the process applied to some other photos going from left to right (click on any of the small pics to see in more detail):
This process works well when you want to show the features of the subject in a good amount of detail and would give small sized photos in online shop listings the edge by helping the subject pop against its background.