adiós (m) - good bye
chau (m) - ciao
despedirse - to say goodbye, to take leave of someone
encantado (m) - nice to meet you
gracias (f) - thank you
hasta luego - so long
hasta mañana - see you tomorrow
muchas gracias (f) - thank you very much
mucho gusto - nice to meet you
nos vemos - see you later
nos vemos en veinte minutos - see you in 20 minutes

Of course, you can also say:
hasta pronto - see you soon
nos vemos - see you
nos vemos pronto - see you soon
hasta pronto, nos vemos - see you soon