On my last visit to Saudi (September 07) i managed to get a brand new ‘Mobily’ pre paid SIM card from a cleaner in the immigrations hall. He had a stack of them.
It cost me 120 saudi riyals which is about $30 US. It came with 100 riyals of credit.
I slipped it in my phone and it was activated immediately. This is useful for calling your local contacts and giving to people back home etc.
The SIM roams internationally too.

The Coffee Trader – as well as doing fine lattes etc and cakes – also offers free super quick WIFI access.
You can find the Coffee Trader opposite Al Kheidma restaurant off Hadda Street in Sana’a.