onOne Software has one of the best tools for resizing images I have found, Genuine Fractals:
Now onOne has bought Liguid Resizing technology which will bring a revolutions not just to downsizing and upsizing software but also advanced retouching/editing as well. See here for a astonishing video demo of the technology. onOne will have a demo of this technology available on its site in early February for free download and testing and a plugin available by mid 2008. I suspect savvy photofinishers will certainly will want to take a look see.