Well your hotel will run some trips probabley to sousse and monastir they will prob do a sahara trip too which lasts a couple of days,but it depends on what you want to see....for instance if you just want to have a walk around sousse jump in a taxi(under 10 dinar) they will drop you off in the centre and go for it,just watch out for people pretending to be your cheif of waiter dont be taken in by them....they're are some wonderfull sights...(get a couple of tunisia guides before you go...and monastir (6 dinar ish) is smaller so it might be better to start there.....the sahara trip is about £130 but by all acounts well worth it if you look at the reviews...how long you staying.....i am right its the sahara beach in scannes that you are staying at?

Ii did the 2 day Sahara trip with Saphir Voyages which was under £70 and very enjoyable. I booked them independently on the phone when I got out there and they picked me up from the hotel. You can get to Tunis and other places by train from Sousse if you fancy being independent.