www.germesia.com - use it and love it
www.apscripts.com - like the looks of it but have never used it
www.comusthumbs.com - use it and find it can be difficult
If you get Comus pay to have them optimize it. If you get APScripts have them install it. If you get Brownie they will install it for free and they will answer any questions you have very quickly either by email or on their BB.