Good news for people who use Skype: You can send SMS text messages to your friends’ mobile phones from within Skype. You need to have Skype 2.5 for this to work. For Mac users with the beta (pre-production) version of Skype 2.5, you can also receive text messages in Skype, so your friends can reply to you.
To send a text message from Skype, go to the Tools menu and select Send SMS Message. You’ll be prompted to select the recipients from your address book, but you can only pick from those who have entered their mobile phone numbers in their Skype profiles, or for whom you’ve entered mobile numbers in your address book. Or, you can enter the mobile number of the recipient manually if he or she isn’t already listed.
You can specify whether you want the text message to list your Skype ID or your mobile number as the sender of the message. If you want to be able to receive replies, you will need to have an SMS-enabled mobile phone.
This is a convenient way to send a message to several people at once, since Skype lets you enter multiple recipients.
Note that you will need SkypeOut credit to send SMS messages. Skype charges a tiny bit less than 13 cents per text message ($0.129 to be exact).
More info on Skype 2.5 for Mac: Skype adds SMS to new Mac beta