On December 12, 2008 ABSoft's noise-reducing 64-bit Neat Image was released; Neat Image is "indispensable in low-light (indoors, night, no-flash, astro) and high-speed (sport, action, children) photography."
Pixel Genius has come up with beta 64 versions of PhotoKit and PhotoKit Sharpener that can run on Photoshop CS4 64 bit installations.
Unless you have upgraded, the most recent version cannot be used when Photoshop CS4 is running as a 64 bit application.
Topaz Adjust v2.5, released in October of 2008, "makes it easy to creatively adjust photo exposure, detail, and color for photo correction and effects."
HDRSoft's tone-mapping Photomatix Pro runs in 64-bit environments however "the current version of Photomatix Pro does not yet take advantage of the 64-bit capability."
SymmetryShop 2 by Artlandia has been updated for CS4. SymmetryShop 2 lets you "easily make more sophisticated patterns, from a greater variety of objects, faster than ever before."
PictureCode's Noise Ninja is "a must-have tool for anyone shooting in low-light or fast-action situations — including news, sports, wedding, and event coverage." The 64-bit version is in beta and can be downloaded from their site.