it's fairly standard to separate the username and password into multiple instances or (better) multiple forms of communication. Some send two separate emails (lol), some send an email and a phone call for the password, you'll find all sorts of methods for separating these. But a couple things should be kept in mind.
1) any password written anywhere or sent via any method in plaintext should be assumed compromised.
2) you can help mitigate #1 by sending a temporary password, requiring the user change it on first login, else expiring in 24 hours or such
while I would follow common sense while conveying passwords, I think the end user is the highest point of risk, not the act of getting it to them.
FWIW, I've seen more than one phone company print sms msgs on the bill.... at least skype should be an ssl connection.