I got a kind of unusual offer notice... a "pre-order" for Acronis True Image Home 2012 combined with Malwarebytes PRO for $25 total. You have to pre-order before 31 Oct 2011 and the license keys will be sent on 31 Oct: http://www.acronis.com/promo/halloween/
I have no experience with True Image Home 2012. Like most backup software some people seem to like Acronis a lot, but others seem to hate it. 2012 looks like a very new release.
Malwarebytes seems to be nearly universally well-regarded. $25 is the regular price for Malwarebytes.