So, today's morning (well, not a very morning .. almost 14:00), I sent about 20 text messages to the people I know + I have their mobile number (most of them are Thai students in Edinburgh). The message is a Firefox advert "Safer, Faster Web browsing ..." along with http://GetFirefox.com url.
Hope it helps.
P.S. This is also another way to use up all my 120 SMS/month quota -_-" If you have some spare SMS quota, try spread the Firefox word this way. Simply better than pay it every month for nothing.