Free:
XoftSpy by ParetoLogic
http://www.paretologic.com/
Paid:
SpySweeper by Webroot
http://www.webroot.com/land/spysweeperb.php?rc=655
Both of those are good
"SpySweeper by Webroot"
Crap! The free ones are much, much better that this useless piece of crap.
I have had it installed since this past July and have yet not had a signature definition upgrade because there have been none available.