Here are some helpful links and tips for helping secure home networks.
Firefox: For the safest browsing around. Make sure to set your history to clear on exit. See below for suggested addons.
Adblock Plus: The Web has never looked better (and safer).
Noscript: I am always stunned at the number of sites wanting to run a script on my machine. You will be too.
OpenDNS: If you have kids on the web, this is a great resource for protecting them from errant clicks and saving you from hours of re-installing software.
Please refer to the list of Home Security links on the left for more ideas.