I have found that it is not the wifi sites that are dangerous (except for proxy redirects that they get infected with) but the sites you connect to once you get on the web that do the most damage. I typically spend my evenings running software to remove viruses from two to three customer systems running WIndows and almost every one of them is on Limewire, Aries or some other peer to peer (Virus) sharing service.
As far as what to do to prevent your computer form getting viruses... get off Windows unless you run it virtually under another OS. I moved my laptop to linux about a year ago have not been happier. Fedora Core 12 is a stable OS with excellent resources, good wireless and other driver support and 99% of the software is FREE... Open source versions that work faster and better than the Windows versions. The only reason I still use Windows is for my games but I run those in Sun/Oracles Virtual box in a virtual XP system that is blocked from internet access unless I let it. My computer boots faster, actually multi-tasks and is virus spyware and adware frre. Unless I am mistaken there are only about 30 Viruses for linux, compared to more viruses than people on the planet for Windows, because they just can't spread (unless you use weak passwords and then you deserve it).
I'll get off my soap box now and wish you good luck with your endeavour.