Sicily

Salerno?? Four hours or road time, plus the half hour ferry, plus the wait for the boat which runs every three-quarters of an hour. Google maps will do it. So will viamichelin.com. They both suck in both directions - - underestimate for back roads, overestimate for freeways. I didn't get an estimate from either, but I kind of like the idea of betting on myself.

At least 4 hrs from Salerno to the Ferry. 1 hr for the ferry crossing (best case scenario). I wouldn't stop in Messina. Nothing there. I'd proceed. In less than 2 hours you can be in Palermo from Messina. You could stop at Cefalu for a couple of hours on the way from ME to PA. Stay in or near Palermo one night or two. You can visit Palermo in a full day. The drive to Catania is about 2 hours by freeway. I would visit Taormina instead of Catania. You can stay at Giardini Naxos down the hill if Taormina is too pricey. I don't know how much time you have for Sicily but Sicily is a huge Island bigger than Massachusetts with lots of historical and tourist sites such as Palermo, Cefalu, Monreale, Erice, Zingaro Reserve, Segesta, Selinunte, Valley of the Temples, Syracuse, Noto, Ragusa, Piazza Armerina, just to name a partial list. If you have less than a week I wouldn't bother.

Robbie, try distancecalculator.globefeed.com/italy to get distances.

Don't stay in Messina. It was interesting to me because my husband's mother grew up there (and her twin sister still lives there), but I don't think a tourist on their first trip to Sicily would think they had seen very much (or enjoy themselves) if they stayed in Messina. (The hotel choice there is lousy too. We went to one of the "nicer" places, and it was much more like one of the "cheaper" places anywhere else. Terrible quality and terrible value for money.

Don't do it. There, you have been warned. Dull, monotonous, dangerous (imagine going head-on with huge trucks and only a line of cones between). Get the overnight ferry Salerno-Palermo (or Termini Imerese) which will cost you almost a couple of hundred euro with cabin, but you'll be spending the same on gas (welcome to Europe!)
All driving times for Sicily are inaccurate (generally increase by 50% if using googlemaps, or 30% if using mainly autostrada).

Ditto Roberto. slow down. smell the roses. Messina sucks, use Trip Advisor to find good lodging at the your price point. Consider a stay at an agritourismo.

Stay in Taormina! It's beautiful, though touristy, but has wonderful Greek Ruins, nice hotels, wonderful restaurants, and is close to Mt. Etna.

One more voice to the choir: every single place in Roberto's post is better than Messina or Catania.

If you don't want to stay in Taormina, the little town of Naxos is very close by (but you won't have to drive up mountain roads). It has the quaint factor but not as chic as Taormina (which you could visit in a half-day). Lots of moderately priced B&Bs.

We drove from Monte Cassino to Messina in about a day.