Out of curiosity, what is "casual DNS serving"? :P
A "technical term". Will explain at the next NZNOG meet if I ever get to go to one...
I assume you mean to ask what a good open DNS recurser is? (recursor?)
Let me turn that around - what are you trying to achieve that you don't by using your ISP's recursive DNS server? (that's a much better than recurser)
For those situations when either the ISP is known, but there are DNS problems, or when it isn't, and you'd want to try with another server.
One of those things that I've come across a great many times lately, with subcontractors putting in 8.8.8.8 etc as a QAD fix.
--
Juha