Free editors I can highly suggest that work with RAW files are
Google's Picasa and
IRFanview, though the latter requires you install some plugins (just a tiny separate file you'll need to download from their webpage). Nikon's ViewNX2 has it's following but I find the interface abominable, personally. Still, that's just my opinion and ViewNX is a very capable editing package that's also free.
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But beginners unfamiliar with the Raw process don't always realize the full story.
Editors like Irfanview, Faststone, Picassa, even ViewNX2 (which is truly abominable) - these might be said to be "editors", and they might be able to"read" Raw files, but they are anything but Raw editors. All they can do is read the Raw file, let you apply some edits, and then save a JPG. Next time you open that Raw file, there are no traces of the previous editing.... So you have to do it again, or you use the previous JPG file, which is then NOT lossless editing. They are not Raw editors. I doubt they are 16 bits. There is no advantage of Raw using these editors. You would be ahead to start with JPG.
Adobe and other actual Raw editors are very different. They save a list of your changes, and next time, you do start again with the original Raw file, and that previous change list is applied automatically (to the view you see). But when you change that edit, you only change the list, you are not shifting image tones over and over, back and forth. You output your final decision as JPG one time (tones shifted one time, only this one set of JPG artifacts are added). If you change your mind later, you discard that JPG (expendable) and start over with your original Raw file and the change list. This is Lossless editing. One could go on and on about the virtues of this, but we gotta understand the difference is day and night.