If you look on Thomsons web site,go to excursions,then Tunisia and you will see what excursions they are doing and prices,A good one is Lights and Lasers,an evening show,excellent.Trips are expensive with them,one year we had a taxi for the day and travelled to all the places we wanted to visit,saving a lot of money.Make your own way to Monastir for a lovely day out,market day is Saturday,there was 4 of us,we took a taxi there £8 and came back on the train to Sousse about 50p each,then a taxi back to PEK,£2.40.If you want to do camel rides etc,you can book them on the beach,also go to the marina for boat trips.

As Crispy says, you can do quite a few things independently, which is not only cheaper but means you can go at your own pace. Sharing a taxi with another couple makes things even cheaper. Trains and buses are very efficient: have a look at the train timetables I put on here a couple of days ago.