Rome may not have the wide range of hostels on offer in a city like Paris, but there are choices available. As usual with the budget accommodation in Rome, most of the hostels are clustered around the main train station, Termini. Prices are likely to be around €30 per night.
As usual when staying in hostels, be prepared to lose a little of your privacy, in exchange for the improved opportunity to mix with fellow travellers. If you have valuables with you, ask the staff if there's somewhere secure you can leave them.
Via Marghera, 8
Tel (+39) 06 4470 4553
The beehive combines the privacy of a small hotel with some of the social aspects of a hostel; there is also a shared dorm room available if you're on a tight budget (and apartments if you're not!).
Hotel des Artistes
Via Villafranca, 20
Tel (+39) 06 4454 365
www.hoteldesartistes.com for hotel rooms
www.hostelrome.com for hostel rooms
Hotel des Artistes is family run, offering hostel accommodation and a selection of nicer rooms.