Most tourists will be interested in accommodation in either the Medina or in Ville Nouvelle. The medina includes the youth hostel and several other budget accomdations, and the high end Dar El Jed. The Ville Nouvelle offers a large number of budget and mid-range accomodation, many grouped within a few blocks of each other north of Place Barcelone. Some places expect couples to present some sort of proof of marriage in order to rent a two person room.

Budget
YHA Tunis Auberge Medina, ? +216 71 567 850. Also referred to as Auberge de Jeunesse and Tunis Youth Hostel. Buried deep within the Medina and a bit of a challenge to find (although there are intermittent signs along the way), this former palace of a sultan is architecturally impressive. Rooms are basic and cooled only by fan. The included evening meal is filling. Breakfast, a simple affair of French bread and coffee, is a bit ropey and is served in the large open courtyard. The communal bathrooms, however, are not cleaned regularly, and may border on offensive. The shower times are limited to an hour in the morning and at night, though hot water may not be available at these times. Plan on using the local hammams for all hot water and cleaning needs. 8TD incl. breakfast.

Mid-range
La Maison Doree, 6 bis rue de Hollande, ? +216 71 240 632 (fax: +216 71 240 631). This hotel captures a slightly faded, colonial era charm. Rooms are basic (the hotel building is old) but clean. Excellent restaurant with bar (2.5 TD Celtia) that provides room service. Breakfast is included in the price, and the croissants are better than average. Rooms come with ensuite sink and shower, but shared toilets - a room with a toilet is an extra 10 TD. Some rooms overlook the local tram, which can be excessively loud - you may want to look out the window to the street below, and possibly listen to the noise of the passing tram. Located half a block north of Place Barcelone. 32-52 TD.
Hotel Transatlantique, Rue De Yougoslavie 106, Tunis 1000, ? +216 71 334 319. Ground plus four levels, the first three accessible by lift. Nice mosaics. Lots of lounge space near the lobby. A little noisy, but nicely located. There is a roof accessible on the fourth floor (turn left after climbing the stairs, walk to the end, and open the unlocked door to your left): good for fresh air or some sun, though the view is not brilliant. Disinterested management. Poor water pressure observed on level 4. 40 TD (Dec 2010). 

Splurge
Dar El-Medina, 64 Rue Sidi ben Arous. A luxury hotel in a century old mansion in the Medina, this is best accessed (at least until you get your bearings) by taking a taxi to Place du Government on the West side of the Medina - it's a few blocks walk from there. 200-250. 
Sheraton Tunis Hotel and Towers, Avenue de la Ligue Arabe · B.P. 345 · Tunis Carthage Cedex 1080, ? (216)(71) 782 100.   Modern hotel overlooking the entire city. Conviently located in the Central Business District.