I really struggled to find much information on trips in advance, so i hope this helps - these are the trips offered by Thomas Cook in November 2012 with adult prices (children half price).
Obviously some if these you could do more flexibly and cheaply under your own steam, with a bit of research.
Sahara Explorer - 2 days, El Djem amphitheatre, Matmata (star wars pit houses), riding camels on Sahara sand dunes, very nice hotel, salt lake, horse & buggy ride through date oasis, 4x4 drive into mountains & Chebika desert oasis, brief stop at Kairouan. 179TD + extra for camel riding.
Tunis medina, the amazing Bardo museum, roman ruins at Carthage & the pretty blue & white village of Sidi Bou Said - an easy way to see a lot in one day. 84TD
El Djem & Kairouan 72TD
Local market & vineyard 55TD
EL Djem & pirate ship 70TD
Dougga & Thuburbo Major roman sites 75TD
Sousse medina 20TD
Berber villages by jeep 75TD
Camel ride + horse & carriage ride 38TD
Friguia Park animal park 45TD
El Djem amphitheatre 45TD
Pirate ship boat trip 35TD
Aqua palace (PEK) 25TD
Catamaran trip 25TD
Reps cabaret & drag act all inclusive 70TD
Alzahara sound & light show with meal & wine 70TD
African dream, animal park then meal with entertainment 70TD