If you ever need to use dig, nslookup, or nsupdate, the Ubuntu package to install is dnsutils.

apt-get install dnsutils

After installation you should have access to:
usr/bin/dig
usr/bin/nslookup
usr/bin/nsupdate

nslookup is very nice for doing reverse URL lookups. By giving it a URL you can get back an IP address. Just go to the command line and type:

nslookup www.yourwebsite.com

nslookup www.slashdot.org
Server: 192.168.0.1
Address: 192.168.0.1#53
Non-authoritative answer:
Name: www.slashdot.org
Address: 66.35.250.151