Controlling image size

I am trying to create a column of images along the right side of the page and I want to use a uniform width. I can set the width of images but not the height, and images that are less than that width are not expanded to fill the space. Is it possible to create square or fixed-size thumbnails, a la image module thumbnails? Otherwise I have to create images for this space that are either horizontal or square. Alternatively, is it possible to use the Image module thumbnails to populate the column?