You have to make them by hand. I make every single thumb I do by hand. Takes longer but much better results. It is called "cropping" the images. Take this gallery for example. http://www.danniashe-freepics.com/white/gallery.html
Ramster, have you done a comparison? Making thumbs by hand seems to be a pain in the ass. Wouldn't you be able to make more galleries thus make more money by using software to make your thumbs?