Here ya go, I just wrote these up for a guy the other day and saved them for such an occasion.
"Move your mouse over your picture in photobucket and a menu will drop down. In the blue bar right under the pic you will see "Share/Edit/Delete/Move" click on "Edit"
When the picture comes up on the edit screen, you will see a series of buttons at the top as follows "Auto Fix/Red Eye/Crop/Resize" click on "Resize"
Then you will see 2 sliding buttons to the upper right next to the size dimensions. Move the height and width buttons until it says 640 x 480 and then just to the right of the buttons you will see 2 check boxes. The first box says "Use Percentages" and the other says "Keep Proportions" you want to check the "Keep Proportions" box. Then go down to the bottom of the page and click "Replace Original" this will resize the picture so you can copy it here. As long as that box that says "Keep Proportions" remains checked, all your pictures that you upload to Photobucket in the future will automatically be resized to those dimensions."