Today we went to Pompeii. I am going to write less about my personal experience and more in the style of a travel help.
There is no need to book any planned excursion from Sorrento to Pompeii. We took a taxi from the hotel to the train station (the hotel can book us a taxi to anywhere in Sorrento for 12 euro), then bought a return ticket on the commuter train to Pompeii, which cost 3.50 euro each. Sorrento is a terminus for the Circumvesuvian train line, so there was a train waiting for us.
The journey took maybe half an hour; at first the train was fairly empty but it quickly filled up. A group of musicians (two accordions, sax and tarbuka drum) started walking through the carriages and playing, making it almost obligatory to give them a few pennies. After they got off the train, a child started playing a toy accordion - not tunes, just odd notes up and down the keyboard. He wore a worried look and looked like an urchin. We tried to develop an understanding of why he might do this - did he need some extra pocket money? Were his parents so poor that they were dependent on the almost non-existent musical skills of this child to earn a few euros so that they could put food on the table? No one (that I saw) gave him any money which probably contributed to his gloomy expression.
Once we arrived at Pompeii, we walked maybe 100 metres to the entrance to the ruins. From the moment that we stepped off the train, we were bombarded with calls to hire guides, buy books and souvenirs, etc. We ignored them. A ticket to the ruins costs 11 euro per person which has to be paid in cash. There are free guide books and a map. There are also guides offering their services, either to groups or to individuals. We did neither. There are enough tour groups wandering around the huge site that one can easily attach oneself to a group for a few minutes, hear an explanation, wander around some more, hear another explanation, etc.
In a sense, the ruins themselves are fairly self explanatory. They also cover a great deal of territory - after all, this was an entire town destroyed. The basilicum (church) is fairly big but the forum is huge. On the other hand, individual 'houses' are very small.
It was very hot while we were there and very little shade; despite that, we saw many people with uncovered heads who weren't drinking water. I wish them well.
After about two hours of wandering about and seeing the sites (including a warehouse in which are stored hundreds of utensils, along with a mummified boy and a dog), we decided that we had had enough. The exit from the site is not where the entrance is, a fact which confused us slightly. Here again, there were several stalls selling the same souvenirs; most of them had very pushy owners. We ignored them and went to the end stall which had a proprietor who was truly glad for our custom. We bought the obligatory shirt, magnet, post cards and book and had a short conversation with the stall's owner; I didn't catch whether the places were allocated randomly or whether the rent changed according to position (and of course, her English wasn't really up to such economic concepts; I was trying to read between the lines).
We had a short walk back to the train station, where after a short wait, we boarded the already full train from Naples back to Sorrento. Fortunately there were just enough empty seats for us to sit. Also boarding was the child with the accordion - along with his mother. We were able to see her persuading him (against his will) to display his meagre talents whilst walking up and down the aisles. This was almost a scene out of Dickens.
Once we arrived back in Sorrento, our first of call was a restaurant; then we went back to the station in order to find a taxi which would return us to the hotel. The fare was an astounding 21 euro! I had previously thought that the 12 euro that the hotel requested was expensive. When we talked to the desk clerk, it turned out that the hotel has an arrangement with a company to transport guests from the hotel at a reduced rate, but that they are not allowed to return guests from random locations to the hotel. This is a pity.
In the evening, we walked back up to the town and went into the Villa Fiorentino, which is a large house with grounds (and almost directly opposite the mobile telephone shop). They are housing an exhibition of Picasso from various stages in his career, although it turns out that almost all of the exhibits were etchings, most of them erotic and few of them interesting. The only room which caught our eye was one housing natural history etchings from 1942; these were excellent (but hardly what one would have expected from Picasso).
As we exited the house, we noticed that the weather had begun to turn: the wind was blowing and a few drops of rain had fallen. We quickly turned into the English Inn again, and just as we did, a thunderstorm began, complete with lightning, thunder and rain. This must have gone on for about half an hour and quickly emptied the streets. After we had eaten and the rain had almost disappeared, we came out and bought umbrellas at a shop doing a roaring trade. Almost immediately, the streets were filled again with people.