Best file format to save as?

Hi all,
I have a Nikon D70 set to RAW file. This creates the files with .NEF extension. I'm sure you are aware that ps can open this type of file, but cannot save as .NEF . My question is really what is the best alternative?

I ask this because when printing large pictures (30"x20") that I have edited, and saved as jpeg the image quality is comprimised and 'grainey'. Is there a file type that will not compress the picture and keep the original clarity?

Many thanks for advise.

Hello,
jpg compresses the crap out of files, witch is great for the web at 72 dpi, but stinks to high heaven printed.

A better choice would be tif.