Most domain registrar websites have a facility like this, but there are also a lot of dedicated websites for performing whois and all sorts of other searches which can tell you who owns and maintains domain names just by typing in the domain.
For Australian domains, in particular, there is Ausregistry.
http://whois.ausregistry.net.au
Some sites enable you to do multiple lookups, such as www.whois.com.au
For worldwide searches there are sites like www.whois.net
