Off the top of my head, I think the Mexican and possibly Spanish navies used the MD500 ASW. It's certainly useful for a small ship (and a damn sight better than nothing), but it's really close to an old-style "manned-DASH" type machine. The mother ship would work up the initial contact and the MD500 would then go and drop a torpedo on it. The difference between the MD and say, a Wasp, is that the MD could localise the contact a bit more precisely using it's MAD bird, thus making it less likely that the torpedo would be wasted by being dropped outside limits. The MD also has a radar, but that's really more relevent for non-ASW missions.
Alouette IIIs have been used on board ships, and IIRC, there are some FACs (Bahraini?) that can carry a Bo-105. I don't know how much ASW gear either of them carries though.
