Well, I can think of two right off hand that should do it.

Image Magick and the Gimp.

But the question of "why?" comes to mind.

-- 
"My new computer's got the clocks, it rocks
But it was obsolete before I opened the box" - W.A.Y.
Margus Ramst wrote:
You can do this in any decent paint program, but I doubt there is an app that
does it automatically...
It would be nearly trivial to program such an app, though. If you can't do it
yourself, perhaps bugging some programmer type would help :)

Margus

Crunchy Frog wrote:
>
> Example, I have 10 BMP files that I rendered using POV. They are
> explod01.bmp through explod10.bmp, each 64x64 pixels. I want to create a
> bmp that is 640x64 containing all of the images so i can load them as
> one file to use in my own display mechanism.
>
> I understand that if the images are 256 color that some color averaging
> will need to be done, but my primary interest is just to physically
> place the images side by side.