Hi to a fellow Mac user!
At the moment we're lucky as we're such a small target that there really aren't any viruses aimed at us but it will happen one day. We're immune to standard PC viruses.
I've used Norton Antivirus which was good.. but I did find (we had it on 7 Macs at work) that sometimes it conflicted with PDF-making. If you're not into that sort of stuff then you should be fine. Certainly the Norton Personal Firewall is very good.
I'd check out the Apple website in the Discussions and see what seems to be most popular. You could post a question there and any number of Mac superbrains will help you.
Just for info, the official line from Apple's site is:
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Mac OS: Antivirus Utilities
Apple encourages the widespread use of multiple antivirus utilities so that virus programmers have more than one program to circumvent, thus making the whole virus writing process more difficult. Here are some of the available antivirus utilities:
Norton Anti-Virus for Macintosh (formerly SAM)
Publisher: Symantec
License: commercial
Virex
Publisher: McAfee
License: commercial
This article provides information about a non-Apple product. Apple Computer, Inc. is not responsible for its content. Please contact the vendor for additional information.
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Hope this helps.