You'll want a DNS server. DNSMasq is quite easy to use and is in the apt repository on Ubuntu (
apt-get install dnsmasq) and believe it's an option during the install you can check off.
It will also do DHCP and will append hostnames to your DNS suffix (i.e. yourcompany.local or whatever) when leases are obtained, so helpful for workstations too.
Obviously you'll need to set all your servers/machines on your network to use the IP of the server you choose to run DNSMasq. It started life as a caching DNS forwarder, and does a very good job of that, but you can do things like use the
server directive to specify forwarders for specific domains (i.e. if you have a corporate DNS server that's authoritative for some other domain i.e. for resolving requests over VPN, etc.).
You also need to specify upstream DNS servers: Google Public DNS (126.96.36.199/188.8.131.52), OpenDNS (184.108.40.206/220.127.116.11), your ISP's DNS servers, or perhaps your router; basically whatever you use now is likely fine.
The docs and
dnsmasq.conf are quite easy to follow; should be fairly straightforward to setup.