After the signature usually nothing, before the signature, it depends:
Sinceramente ---> Sincerely (formal/business letters)
Atentamente ---> Attentively (formal/business letters)
Amistosamente ---> Friendly (informal, rarely used)
Saludos ---> Greetings (Friendly, formal and informal)
Muchos saludos --> A lot of greetings (Friendly, formal and informal)
Abrazos/Un abrazo ---> Hugs (Informal, very friendly, usually for people you know, friends, family, etc.)
Besos ---> Kisses (obvious)
