http://www.intego.com/  Intego VirusBarrier for Mac.  When I bought my very first Intel macbook the only thing in the Apple store was the norton software but it didn't yet have a universal binary.  McAfee had a mac antivirus software but they only sold it in packages of three. 

I looked around and found a really good 3rd-party review for Intego.  I've used them on my Macs for years.