Etisalat (GSM) in UAE offer a ‘Wasel’ card which is for travellers and visitors. It is very easy to get one and you can get one on entry at all airports and at the major shopping centres.

Wasel cards are prepaid and can be bought in 25 and 40 AED denominations. To keep your Wasel card activated you have to pay a renewal fee of 100 AED a year (about $30 US)
The Wasel card should roam automatically if it is still activated with credit, but check with whoever you are buying it from.

Etisalat provides an excellent ‘my account’ feature so you can add credit to your account and also renew the annual fee.

Read more information on Etisalat’s website