What is the other applications of a DNS servers have besides giving canonical names to IP #s?

What can I use it for in my LAN?

How can it help me?

Resolves human readable hostnames to IP addresses
Caches previous DNS requeries locally so you don't have to keep hitting your ISP
Can allow for CNAME alias's, giving multiple hostnames to one IP address

If you run a domain environment, Active Directory requires DNS in some form.

The best use you can get running DNS server is faster queries
since the server you are going point to, is in your LAN.

It also: "eliminate the need to have (and manually update)
a HOSTS file on each system on your LAN." <-- Taken
form the about Debian Linux web site.

As for how can you use it, and more ways you can benefit from
DNS server, Google for: "dns and bind pdf". You'll find all
you need to know about DNS service on the first few chapters.

-W

What do you mean "domain environment" persay?

Do you mean Windows Domain? And by the way, can something like that be done in Linux.

Linux Domain Server for Windows clients to connect to...

A "domain environment" is the Microsoft term and means that your client PCs belong to a Domain, most typically Windows. Samba has the ability to work as a NT4 style PDC (primary Domain Controller) for windows. Samba-tng can operate as a Windows 2000 Domain Controller, but I don't believe they can be the PDC-emulator for the domain.

-- edit --
Also, running DNS gives you the ability to remove the NETBios protocol from your network as NETBios is chatty and unsecure. Typically this is done on a per client per NIC basis under its advanced properties. If you remove NetBios without DNS on your network, you completely remove all name resolution.