On my digital SLRs, I've been shooting RAW files for quite some time now in order to get the most out of my images. However, I've had some concerns about being able to read these files later, so I've started converting all of my RAW files to Adobe's digital negative format DNG. I figure with Adobe backing it, it's more likely to be supported in the future vs. some random old Canon file format.
However, one my frustrations is that there hasn't been a free, Adobe codec for DNG for Windows 7 (especially 64-bit); this prevents me from seeing thumbnails in Explorer or from seeing the images in apps like the nice Windows Live Photo Gallery.
Well, my wait is over! Adobe Labs has a release candidate codec available now for 32 and 64-bit Windows 7 (Vista is not supported). It seems to run fine, albeit a little slow. (No word on their site about when they'll have their final release.)
You can get it here.