On Mac OS X, you can use them just for specific domains. For example, create:
/etc/resolver/bbc.co.uk
with the contents: nameserver 208.122.23.22
nameserver 208.122.23.23
And now you'll be using unblock-us's name servers for just bbc.co.uk and its subdomains. You could do something similar for your entire network with dnsmasq.