Very cheap places to stay while having a trip in Rome...
* Litus Roma Hostel, lungomare Toscanelli 186. The first hostel by the sea in Rome. Located near the new port of Rome and close to the excavations of Ostia Antica. it's easy reachable from the center of Rome by underground. Over 140 beds in comfortable rooms with ensuite bathrooms, TV color and a aview of the sea. http://www.litusroma.com
* Agli scavi di Ostia Antica, Via della Stazione di Ostia Antica 7. A small ville steeped in the green of the roman campaign. It is located at only 100 metres from the archeological excavations of Ostia Antica. At about 50 metres from the bus and the train stop. http://www.ostiaantica.net/bandb/
* Apartment Filippus Spanish Square, Via Casini,  It is a 110 square meters apartment, with a wonderful terrace,simply lovely, and it is composed by the entrance room, two big double bedrooms ( one has a closet ), bathroom with bath/shower, very big living room with double sofa bed and fan on the ceiling, fully equipped kitchen.
* Alessandro Hostels, Alessandro Palace - Via Vicenza 42, +39.06.446.1958 fax +39.06.493.80.534, Alessandro Downtown - Via C. Cattaneo 23, +39.06.443.40.147, Alessandro Indipendenza - Via Curtatone 13, +39.06.44.61.958, has grown from a pensione into a small chain of three of the most popular backpacker hostels in Rome. All locations are 5 minutes on foot from Termini, include free breakfast, no curfew, cheap internet, video security, free pizza parties at the Palace pub, and free linens. Other amenities vary between the locations (ie the Palace has ensuite bathrooms and an in-house pub with cheap beers, while the Downtown location has communal bathrooms and a medium sized self-service kitchen.) Prices from €16 per person per night in low season, from €19 per person per night in high season. http://www.hostelsalessandro.com/
* Freedom Traveller Hostel, Via Gaeta 25, (+39) 06 47823862. A four-minute walk from the central train station, this hostel has adequate dorms from €23 per night, including free breakfast, internet and dinner. Some dorms also have nice balconies, kitchens and communal areas. No curfew, but lockout is from 11.00 - 15.00. http://www.freedom-traveller.it/
* Gullivers House, Via Palermo 36, (+39)-064817680. Small co-ed youth hostel. 10 minutes from Termini. Owned by a nice couple, fluent English, they'll help you plan your stay in Rome better then any travel agent would. Free breakfast is what you would expect, so not much. They do have a fridge you can use, buy some juice from one of the nearby stores for a refreshment when you get back in the evening after a long day of not drinking the €2 cokes. Show English-language movies in the evening. Clean. Cute dogs. http://www.gullivershouse.com
* M&J Place Hostel Roma, Via Solferino , 9, (+39) 064462802 (info @ mejplacehostel.com) is within spitting distance of the train station. Friendly staff and reasonable dorms, this popular hostel has a paltry free breakfast but no lockout or curfew. http://www.hostelinrome.com/
* Yellow Hostel, 44 via Palestro, 00185, telephone: +39 06 49 382 682 ( info @ yellowhostel.com ), dorms from €23 per night. http://www.yellowhostel.com/
* Colors Hostel on the West side of the city, a few blocks north of the Vatican (take the metro from the train station, which is on the East side of the city) http://www.colorshotel.com/
* Pop Inn Hostel Very clean & comfortable environment, & all our bathrooms are kept spotlessly clean so that you don’t have to be worried if you want to book a room with shared bathroom. All of the rooms are freshly cleaned everyday & the beds made. We have fans in the summer & in the winter heaters keep the rooms warm and cozy.
* YWCA Foyer di Roma Youth Hostel is four blocks from Termini on the Via C. Balbo. Rooms are spotless, bathrooms are extremely clean, and towels and linens are changed once a day. Internet for €1 per hour. Fridge on every floor. Continental breakfast included in room rate. €26 per person per night for a bed in a 4-person room. €31 for a double, €47 for a private room. You have to be female to reserve a room; however, men can stay if accompanied by a woman. Via C. Balbo 4, 00184, telephone: +39 06 4880460 (firstname.lastname@example.org).
* Cristina House Located in the area around Termini Rail Station, Cristina House is a group of Hostels, Bed&Breakfast and Low budget-Hotels. Web site provide more information and FREE online booking system. http://www.cristinahouse.com/