I ran across a great tool by MikroTik which will map your network and then provide service level monitoring and alerts all for free. Check this out in the "Free Security Tools" > "Network Tools" section.
This is a security guide for home computer users and is 136 pages in PDF format. There is a lot of valuable information along with links to free tools and web sites. Why pay for Virus protection when free versions are available? This is a new PDF version of the security guide with updated links. You can also download the flash movies that were in the original executable version in the downloads section.
This is a ZIP archive of the flash movies contained in the original compiled version of The Security Guide. I am including these to be used in conjunction with the new PDF version.