I used to cover the battery connections with grease to keep them from corroding. Is this still the thing to do? Is there a better cover that regular grease? Is Corrosion still a problem or has someting been added to prevent the corrosion without sealing out the air?
They sell an anticorrosive in the auto parts store, but it just looks like red-colored vasoline (which John Emde suggests).
Corrosion will always occur when you have to different types of metals combined and exposed to air (& charging gases).
It's important keep the corrosion to a minmum, because it will eat away your battery posts and lugs over time AND most importantly, can lead to resistance in the connections. A little resistance generates a lot of wattage (heat) with the high amperages we're drawing.
Combining Watts law P=V *I and Ohm's law V = I * R gives P (watts) = I^2 * R
so a little R gives a lot of P with high I!
Take it from a man that has (unfortunately) melted a few battery posts due to loose connections! :-(