Question

Can I check my Mac for viruses? If so, how?

Answer 1

Being unix based there are not many viruses for OSX. There are how ever worms, trojans and malware. For the most part they would have to be installed by you hidden away in some scam software.

The best thing you can do is to not run in an account that has Admin or Super User privliges. Also keep Java updated and you should be fine.

Answer 2

if you want a scanner so as not to pass on viruses to your Win friend, I recommend BitDefender or Clamxav. It's free and you can get in at Appstore.
I have Clamxav on my mac and scan files before passing them to my friends.

Answer 3

You can use Sophos Anti Virus. It's free and has live protection. Also auto update. I've had no trouble with it.