I have read that, at the time of writing (2013), UAE visas are:
- 96-Hour : Valid for passengers in transit
- Tourist : Maximum 30 days
- Visit : Maximum 90 days
But I am only connecting flights, so I am staying in the airport. And can't find any information regarding that case.
I only could find in the FAQ something implicitely saying that you do not need a visa if stying in the airport:
Can I leave the airport when transiting through Dubai?
This depends on the nationality stated in your passport and on the length of your stop in Dubai. Travellers of most nationalities require visas to enter Dubai, and regulations frequently change, so if you wish to leave the airport while in transit through Dubai, please check your visa requirements with your local UAE embassy before you start your journey. Travellers of certain nationalities may obtain visas at the airport on arrival.