I am always glad to see someone new trying Linux, however there are a few things I would recommend.

If you dive straight into an install of Linux, your not really going to know much when your asked questions about window managers and desktop enviroments.

It can also be a pain at first finding out what software you need, for example, running a webserver.

I would recommend distrowatch - Google IT. It is a website with reviews on hundreds of distros - as well as providing links to download them and to the websites with info about them.

A lot of Linux distributions are free as they are open source.

Do some research first.

Here are some names of server software:

Apache - HTTP Server
MySQL - Database Server
Exim/qmail/sendmail/postfix - SMTP Servers
dovecot - Imap/POP3 Server
Bind - DNS Server
Webmin - A web based control panel - Good for configuring servers.... especially if you choose to install linux with no X Server (No Graphical Interface).

As for cluster software. Do some research on HAProxy, Heartbeat & DRBD. But to be honist, get comfortable configuring seperate machines first. Don't dive in too deep otherwise its a hell of a learning curve.