Calling out all Mac Skype users: check your Skype account for free minutes/SMS on Fridays!
Skype-lovers to-do list:
- go & check on www.skype.com,
- log in with your account data (unless you’re already logged in or you use Firefox)
- get some minutes (or SMSs) for FREE!, should be 15 minutes (but check effective call rates!)
As stated on Skype web site, this will work on Fridays for the full month of December!
Mac users only 
Update: some users pointed out that this offer may be related to selected countries only.
UK, France & Italy seem to be working fine…