Administrative Tools

VMWARE

        First of all i love VMWare, personally i have a bias towards them and their products as I used them on daily basis in my day time job, having said that - at the site mentioned below you will find VMWare Server - this application sites on top of your current OS and allows you to create different OS's within it, can have multiple OS's running within one physical machine, this is great for testing any new tools you might want to try from the open source community. VMware themselves have a download section where you can download pre-made "appliances" that will suit your needs, such as firewalls, monitoring tools, CRM packages..... i would consider getting some kind of brief tutorial on creating new Virtual Machines and how they can interact with the host OS, so you do not end up causing interference with your main OS. Good rule of thumb for any virtual machine server the more CPU and RAM the better, and make sure not to overallocate RAM as to the point where the host OS does not have enough to run - this unfortunately is spoken from experience.

http://www.vmware.com/download/

       VMWare also features a  free iron solution if you will in their product line, this product does not rely on a host OS to sit on top of instead it is it's own OS that VMWare has created, and the interface is accessible via Web Browser, the huge advantage to this product is the fact that the RAM per Client machine  limitation set up in the VMWare server does not exist, so you can create machines with heavier RAM setup - pending hardware and software allows for it...

http://www.vmware.com/products/esxi/ 

Microsoft Virtual Server

         If you already own MS Server then you are entitled to MS Virtual Server, and have the ability to download and create Virtual Machines, you still have to pay for licensing costs to MS, but with some research you can find out exactly what MS policy is regarding one purchased licensed and running a Virtual machine on top for testing purposes, in some cases MS allows you to have a Virtual machine running under the same licence on the same hardware - make sure to check with your MS licensing rep for this. 

http://en.wikipedia.org/wiki/Microsoft_Virtual_Server

Free PC remote control

use this software if you want to be able to login to your PC from anywhere in the world (given you leave your pc on and have a decent connection) - this will afford you a way to control the PC as if you were sitting right in front of it. You have to register on the site and download the client software to your PC, but once that's done, you can access your PC from anywhere in the world with a decent connection. The site will keep prompting you to upgrade, but you can choose the Free option and continue using it.

https://secure.logmein.com/home.asp?lang=en