Well, looks like bad news here for those of you who use sound annotations. In my tests, iPhoto 5 would not recognize the .wav files generated by both my Olympus C-5050 and Contax SL300RT.
There is a workaround here. It could be a whole article, but for now this will get you on the right track.
I thought at first I could just convert the .wav files to .mov files and iPhoto would accept them. But it didn't. I figured out that iPhoto was looking for a video track in the file, not just pure audio. So I added a few seconds of "black" (a 320x240 image using the "Add" command in QT Pro). I then exported the sound annotation using the "Photo-Jpeg" compressor for the video track (the black frame) and "MPEG-4" for audio (formerly the .wav file captured by the camera). iPhoto 5 gobbled it right up, and I could add it to my library.
This might sound like a lot of work, but you could use AppleScript to automate the whole process in just a few minutes. Just keep the file names the same so they match up to the images that the voice notes are for.