SecureMac was historically one of the best sites for information on mac security topics. It has slowed down it's updates in the past 2 years but seems to be speeding up again. Definitely a recommended read.
Quoted from the SecureMac.com site
Welcome to SecureMac.com, a site devoted to Apple Macintosh security and Mac OS X Security! Use the Side Bar to navigate the site, check this page frequently for updates and new security products for the Mac OS!