What custom sound mods are there?

[McChubs]

I recently got Chatterer and found it added tonnes of atmosphere. I know there's a countdown mod (called, appropriately, Countdown...) but are there any others out there? I'd particularly like a mod that added warning sounds, general cockpit background noise, that kind of thing. Anything out there that fits the bill?

[Kerbal01]

There's one for ion engines.