Of Macs and smartphones
If you're a Mac user, chances are you still really don't need protection. Probably. Almost certainly. Ahem. OK, but if you are concerned I'm sorry to report that there are no free antivirus programs for Mac I can recommend. ClamXav, like its Windows-based relative, is just too slow. So, if you really want to be safe, or perhaps protect your Windows local area network neighbors from Windows viruses hiding out in files on your Mac, use either Norton AntiVirus for Mac or VirusBarrier X6.
If you use an iPad, iPhone, or an iPod Touch, you really don't have much to worry about. After all, for better or for worse, every last application you can run has to pass through the Apple App Store. VirusBarrier does incorporate i-device scanning in its program if you want to be extra sure. To use it you'll need to attach your iPhone or what have you to your Mac. It also can't hurt to download Trend Micro's free Smart Surfing, which offers some basic protection from phishing Web sites and the like.
Personally, I don't use any antivirus protection on my iPod Touch or iPad. If I did more random Web browsing on either one I'd add Smart Surfing to them.
Android, I'm sorry to say, is another story. For example, in late February a hacked version of the legit Android app Steamy Window emerged that racks up text message charges and causes other havoc.
There are two programs that you can consider here. One is AVG's Antivirus for Android, which is available in both a free version and a $9.99 Pro version. The other, which is the one I use, is Lookout Mobile Security. It's my favorite because it not only includes antivirus protection, it also comes with an automatic backup function, and, best of all, several built-in mechanisms to make sure it can't be easily stolen or lost. Combine all that with its price, free, and you have a winner.