I would like to offer users the option of sms txt'ing their friends to let them know that a boooking has been made on our site.. UK based

Does anyone know of the best / cheapest / free option to incorporate this in to our site ?

What companies deal with this or what in your opinion is the best option ?

Being able to send to up to 10 people at once ..

[edited by: Lobo at 4:35 am (utc) on Feb. 11, 2009]

[edited by: bakedjake at 5:22 am (utc) on Feb. 11, 2009]