just upgraded from leopard to snow leopard, and cant find iphoto.
Must have been a erase and install, as only OS X is replaced when merely upgraded.
is there a new photo app?
Run the bundled app installer off your original disks that came with the machine, if that doesnt' work, then use Pacifist from CharlesSoft to extract the program off the disks.
Make sure to use Software Update so it get updated to current versions.