I was going to write an article about my experience with each of these but for now I just want a handy list to refer to. These first 4 are actively maintained and what I would recommend for consideration.

• Bind - Debian/Ubuntu package: bind9
• MaraDNS - Debian/Ubuntu package: maradns
• NSD - Debian/Ubuntu package: nsd
• PowerDNS - Debian/Ubuntu packages: pdns-*

There are 2 other open source DNS server projects but they are not being maintained and not well packaged in Debian/Ubuntu and thus should be avoided: djbdns and Posadis.