I use a product called Evaporust. I searched and saw it hadn't been mentioned here. It ain't cheap but but provides the best rust removal I have seen. It basically glues itself to rust and dissolves it without eating at good metal. It is better than Electrolysis because it doesn't cause Hydrogen embrittlement (which causes parts to break). I don't work for them by the way, just really like the stuff. They sell it at Harbor Freight.
DSCN1934 by nwaringa, on Flickr
DSCN1934 by nwaringa, on Flickr