Sardinia or Elba

Sardinia is easy as well, from Civitavecchia, you can take a ferry....a few hours....fun times!

You will need a car in both.
Sardinia is large, almost as large as Sicily. If you have only a few days for the island, you should concentrate in one area only, also because the roads along the coast are curvy, therefore travel times are long. I have experience only with the Northern side of Sardinia where I have been a few times, generally staying in Santa Teresa di Gallura or its vicinity. The white beaches and the crystal clear sea are unparalleled anywhere in the Mediterranean, and probably even beyond. Below is a comprehensive review of all beaches of Sardinia.
http://www.unionesarda.it/collane/spiagge/home_spiagge.aspx

If you stay in the North, I recommend to take a full day boat excursion to the Maddalena Archipelago National Park. Several companies have such excursions departing from Santa Teresa Harbor or from Palau (and also other places in the area). Another nice getaway is a trip across to the fortified city of Bonifacio, in Corsica (France). The crossing on the ferry from Santa Teresa is about 40 min. You can visit it in a day.

If you choose Sardinia, my recommendation is to fly to Olbia or Alghero (in the North) or Cagliari (if you choose the the south) and rent a car there. The Ferry from Civitavecchia is a long 5 hours but also there might be restrictions placed by rental car companies on your ability to take a car on a ferry. Inquire with the rental company and check the rental contract.

Elba is a quick getaway from Piombino. The crossing can be as short as 30 min. (depending on which type of boats). The island is small and you can drive around it in a day (although I recommend to stay at least 2-3 days). Also in this case make sure the car rental contract lets you take a rental car on a ferry.
If Capt. Schettino is at the helm, jump ship immediately :)

If Capt. Schettino is at the helm, you'll be jumping ship eventually so no need to jump immediately. :-)

hi tiffany007, I'm Italian , I live in Rome and I've a home for the holidays in the south of Sardinia (for me and my family I don't rent it ). I know very well all the Sardinia island and I think the south is very beautiful, because it is wild and untouched. Many american people bought a house in the south of the Sardinia because they appreciate beautiful nature, limpid sea, good wine , good food , traditions and friendly people. By plane Rome - Cagliari (around one hour of travel) with Ryanair (low cost ) and car rental in the Cagliari airport , for one week you can spend around 200 or 250 euros for person (plane and car). Any way you can ask me everything if you are interested to going there. You can ask me also if you need something in Rome, I'll be happy to help you in disinterested way and in free way. I hope you can understand my bad English.