Orange Free SMS
Orange is a UK mobile phone network.
Yes, that Orange! (Now EE.) And they offer all Orange customers up to 30 free sms per month - just register with your mobile phone no. This is what it says at their site, once you login (click the "Send a text message" link beneath Mobile Tools):
"Use this page to send a text message to any UK mobile phone. You can send free of charge from this site, however the recipient of your message will not be able to reply to it directly. Alternatively send a text message as if from your Orange phone. You will be charged according to your Service Plan rates"
Got that. Basically, you can send your sms text message anonymously for free otherwise it will cost you, as if you were sending it from your real phone! Hmm.
Anyway, as you'd expect, the sms is delivered almost immediately. 30 free sms is pretty good, too.
Pros: Free SMS site, up to 30 free sms per month, secure and fast service
Cons: If you send from your own number it won't be free (confusingly)