Honestly, the best resize feature on a normal program I have seen is Microsoft Word's. Open the picture there, set the resize dimensions (In XP, right click, format, size; in Vista, right click, size).
After they are the same size, copy them one at a time into paint save it as a gif or jpeg or whatever file type you want to use, and then finally use an online gif animation creator.
(NOTE: it might help if you could crop it a bit too)
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