I just set a size in paint shop pro, do it once and then save the picture. Then just ctrl+y to redo
When I've used this the picture quality is terrible.
I've set up a batch job in Photo Shop which yields far better images.
Microsoft office also has the picture manager which does an excellent job of batches.
You just need to have the office package installed of course.
Do they not re size it for you? I upload my pics onto flicker pretty big and they resize it for me.