I happened by the WinPatrol homepage and noticed that there's a 50% off sale running for the PLUS version:
http://www.winpatrol.com/The free version is pretty good on its own - the PLUS version adds access to an online knowlegebase and some real-time detection of file system and registry changes. But mainly it helps support ongoing development of the program.
The discount ends at midnight EST today (25 Jan 2009) - so there's about 8 more hours as I write this...