How do you say "By the way" in Spanish?

Below is a reprint of the thread I started on WordReference (http://forum.wordreference.com/showthread.php?t=2254465&p=11314044#post1...):

By the way in English has various meanings, among them

1. Since we're on the topic... (e.g. My brother is in town. By the way, would you like to meet him?)
2. Changing the topic entirely (incidentally)... (e.g. My brother is in town. By the way, have you seen Jane?)
3. It just occurred to me... (e.g. Happy belated birthday, by the way.)

How do I translate these meanings into Spanish? My attempt follows:

1. Mi hermano está de visita. A propósito / Por cierto, ¿no te gustaría conocerlo?
2. Mi hermano está de visita. Casi se me olvida / Cambiando completamenta el tema / Me hace pensar, has visto a Jane?
3. Link translates it as "Por cierto, feliz cumpleaños atrasado."