I have an S10 Blazer I was doing some work on, and in the process of putting everything back together I discovered this hose (marked in blue) that smells of coolant, but I can't determine where it's supposed to connect and I do not remember disconnecting it at all. Can someone help me figure out where this goes? It's vaguely S shaped as well.

 

I believe that is the A.I.R. (air injection reaction) pump which is an emissions device. The hose you are identifying is the intake side of the pump and should just run up along the side of the radiator. Depending on whether it has been replaced or not, it could run straight up and have a plastic fitting in the end of it or it could run up along the radiator, turn 180 degrees, then just have a slant cut end to it.