Wombat showed links to some very good free spyware software. But it depends on which ones in particular that you are looking for. Not all are free and some are way more expensive than others.
If you know the name then google is ypur friend.
If not one of my favorite sites for software is
MajorGeeks.com - Download Freeware and Shareware Computer Utilities.
in the left listing is the basis for what type of software that you may be looking for. click on spyware/malware and it will take you to a page filled with them.
click on anti-virus and then be directed to that section.
