Skype rocks!
Can't recommend Skype too highly - slick software and very cheap calls to landlines. I ring home at least once a day when away, often with video link. IMHO, every crew should have one. MSN is a useful backup, since some countries (esp. Middle Eastern) have blocked access to Skype servers.
What I'd love to know is why the assorted domestic disasters (broken teeth, arguments with neigbours, sick dogs, non-starting cars etc.) only seem to happen when I'm away and can do nothing about them?