[LarsB]

Thanks for everyone's help.

rfs - You nailed it. My images looked just like your examples. I poked around in Photoshop, and sure enough, I was using Adobe RGB. I have no idea how that got set, but once I changed it to sRGB, everything fell into place.

Arbib - Thanks for the pointer to Faststone. Some of my images are large enough that Photoshop Save for Web complains, but Faststone handles them just fine. Its a great tool.