My favorites:
TefGel
Duralac
Blue Loc-Tite
All of these do a good job at isolating dissimilar metals...
One's folks claim to work well but one's that I have not had good luck with..
Lanocote - AKA Lanolin
Silicone
Pipe Dope's - various
Greases
Never-Seize type products containing dissimilar metals such as aluminum, copper or graphite...