What's the difference between Prosciutto, Jamon Serrano and Speck?
Differences are mainly a question of origin. Speck comes from Tyrol (it actually means "bacon" in german, which is misleading) and is prepared with a specific blend of spices, usually including juniper, Jamon Serrano from Spain (it means "mountain ham" in spanish) and is a dry-cured ham, and prosciutto just means "ham" in italian.

There are plenty of differences in flavor, consistency and aspect, depending on the difference of preparation: ripening, spices and herbs and so on.