This above link is another courtesy of Jennifer Avventura’s blog.
There are a couple of places we haven’t been to ourselves like Dorgali, Tavolara or the Asinara island. And just one I wouldn’t bother with again (Costa Smeralda. Well, Porto Cervo at any rate)
Jennifer’s explanations are great … I would add that I would also recommend a day trip from Santa Teresa to go and tour the Maddalena islands. Boats to do so come in all shapes, sizes and price brackets. But get to Santa Teresa’s port before 9am to choose your boat .