I have found a few PNG "hacks", fixes, or workarounds so far.  But none of them appear to have worked for me.  Does anyone know of a reliable PNG fix that they are using and would like to share?  :)

First that didn't work:
http://richard-m.blogspot.com/2006/09/ie-55-ie6x-transparent-png-fix.html

Second that didn't work (pretty much the same thing):
http://www.dominoguru.com/pages/12152005115558.html

I am wanting to use some PNGs as background images.  The problem is that the transparency and dropshadow is not properly rendered in IE 6.0.  IE 7 and Firefox are fine.  I haven't checked Opera yet, but I have read that it will be okay there too.  Unfortunately, according to my Google Analytics reporting, IE 6 is still in major use.  :(

I use a program called TweakPNG to fix many of the small problems that I run into.  The most common use for it at the moment is gamma correction so the color renders correctly in IE6 and IE7.  To find it you can type tweakpng into google.  It is a free program that does a variety of things with a png.