I can't believe Johanna Lindsey hasn't been mentioned.
Warrior's Woman is dear to my heart especially. There's also Jean Auel of the Earth's Children(
Clan of the Cave Bear) series. I know that it's mostly a series of books about primative man, but the love scenes are wonderfully over the top. *That* lady has foreplay down to a tasty science.
and call me shallow but I've got a thing for tall sexy primative men...