OK, I have to thank Tortuga at DDN for helping me with this as I only learned how today! This is in Photoshop CS...
1) open the picture you want to have the drop shadow effect
2) Layer -> Duplicate Layer
3) Make your DUPLICATE layer active -> Image -> Canvass Size -> add 30 or so pixels to each dimension (you can adjust this to whatever you want and crop later)
You will now have your image surrounded by a white box
4) Make ORIGINAL layer active
5) Edit -> Fill -> choose your colour. If you are using this on your web page choose the exact same colour as your background.
1) open the picture you want to have the drop shadow effect
2) Layer -> Duplicate Layer
3) Make your DUPLICATE layer active -> Image -> Canvass Size -> add 30 or so pixels to each dimension (you can adjust this to whatever you want and crop later)
You will now have your image surrounded by a white box
4) Make ORIGINAL layer active
5) Edit -> Fill -> choose your colour. If you are using this on your web page choose the exact same colour as your background.