Primary DNS hosting, without transferring the domains

[nik]

How do,

Who do we currently recommend for providing primary DNS hosting, without 
needing to transfer domains?  I've got a dozen or so domain names, and 
as part of my attempt to get out of the hosting-for-friends-and-family 
business I want to shift the hosting elsewhere.

However, I don't especially want to have to transfer the domain name to 
somewhere else, I'm happy with my current registrar.  I just want 
someone to host the primary DNS.

That seems to rule out Easily and Gandi, who seemed to be most 
recommended the last time this came up (as far as I can tell from my 
mail archives).

N