After a little Google searching, I found a product called PhotoRescue. It's basically a disk utility with an OS X version that can find photo files on various media cards. I ran the program and voila -- there were my photos! In a matter of minutes, I was able to save them all to disk and import them into iPhoto with no problems. I suspect that other disk utilities may have been able to perform the same task, but I don't have one installed.
This is hopefully not a program anyone will need to use often - but it sure is nice to know it's there!
[robg adds: PhotoRescue is commercial software, but it has a free "demo mode" that will show you anything that may be recoverable from the card ... so you can try before you buy.]

