Lots of discussion about this on these forums already, but in a nutshell -- if it can soak, like small parts, then Evaporust can't be beat. For frame stuff, oxalic acid. If you google "oxalic acid bikeforums," you will find lots of info. This can be in a kiddie pool or somesuch if it needs to soak, or you can get Barkeeper's Friend cleaner to do spot removal.

Evaporust is non-toxic, but oxalic acid needs more careful handling.