When in Abu Dhabi or even passing through the airport a must see is the Grand Mosque
Sheikh Zayed Bin Sultan Al Nahyan Grand Mosque to be correct. Opens at 09:00. Tours at 10:00, 11:00 and 17:00. Closed on a Friday. Free entry, great for photos and all you have to do is dress correctly. Brilliant tour guide. Its about 10USD from the town and I guess about the same from the airport each way in a taxi, but do check in advance! See the gallery for more photos.
www.szgmc.ae or www.visitabudhabie.ae for more details.