We are planning a 9 day trip to Rome over the Winter holidays, mid-December through Christmas, & need advice from fodorites on day trips. Prefer south of Rome for warmer weather, but interested in hearing about "must-sees" within reach.

Some suggestions for day trips from Rome:
Tivoli (reachable by bus from Rome), visit Villa D'Este and VIlla Adriana.

Castelli Romani (Frascati, Genzano, Nemi, Marino), Castel Gandolfo. Mainly for their wine, good food and some lovely views. Regular Cotral bus service from Rome Anagnina subway station.

Cassino, with its imposing Abbey of Monte Cassino. There is a train connection from Rome to Cassino.

Sperlonga, Terracina, Gaeta, Formia, San Felice Circeo. These are basically seaside resorts, and in november are very quiet, so if you like the sea in winter, that's the place. IMO it's better to get a car for the day because it's nice to drive around the area even if you can get a train from Rome to Formia.
If you start very early in the morning you can take a eurostar from Rome to Naples and spend the day there and even reach Pompeii, even if I wouldn't do it because I don't like to see things with haste.

From Rome you can also visit Ostia for its ruins, you can doa day trip to Orvieto, but it's inland, though very very lovely town. You can go there by taking one or 2 trains if I remember well.

We took a bus to Sorrento and from there a ferry ride to the island of Capri which I believe its a must see. But then again I just realized to are going in winter time so Capri is probably not a choice but Sorrento and Pompeii which is also close to Sorrento is another choice.
Good luck.

For trips from Rome, some are easiest on your own and others on a tour. Some tours will not be offered off season.

Pompeii can easliy be done on your own. Check this sight for the proper way to get there. If you start very early, and end late, you could see some of Sorrento. Full or VERY long day. Keep in mind the train schedules when decide on late nigh returns.

Tivoli Fountains and Villa D'Este and VIlla Adriana (1/2 day)is easiest done on a tour.

Assisi is not north, but doable. Tours will probably not be offered at that time, so do it solo. Full day.

I suggest that yuo do a couple of days in Rome and then a day trip. Another day or so in Rome and the another Trip. Mix up your sights.

Much appreciated! Any thoughts on organized tours?

here are detailed instructions on travel from Rome to Pompeii

http://www.fodors.com/forums/threads...p;tid=34665492

Check with your hotel. They might have a group that they work with. Also, check to net for other sources of groups.