Free SMS Messaging Worldwide
Using SendSMSnow you can send text messages worldwide (although not every network is supported).
Registration is required, but you can send unlimited texts, view a history of your sent texts and receive texts to your inbox.
You can also create a profile, a phonebook and upload photos.
Further comments:
Apparently, it does not work for UK mobile phones.
Registration required, etc:
Registration required? Yes
Receive messages? Yes
Confirmed delivery of messages? No
Message length?
Message Quota? unlimited