Well, for the longest time I would have recommended RAW Therapee, but I recently discovered it wasn't reading my raw files properly from either my D70 or my D7000. The colors were being muted a bit, and the whole image was being darkened, so the luminance histogram was being shifted to the left by as much as a stop and the color histograms were kind of all over the place. If you're looking for something free and don't mind the extra work to compensate for discrepancies like that, it's still got a pretty decent workflow. Otherwise download a copy of GIMP along with a RAW conversion plugin like UFRaw. I haven't used it extensively, but it should do the trick.
Lightroom 3 blows everything away though, it's worth the dough.