Gulliver's House is a small but very friendly affair, right in the heart of Rome's backpacker area. With only three dorm rooms, it's little more than a large apartment tucked into a building; but both the staff and the people are very friendly, and the lounge/TV room is a great place to hang out and shmooze (or to just watch The Simpsons all night). Sadly, as with all good places in Europe, you do need to book this place ahead — but if you're able to plan exactly when you'll be staying there, it's well worth the effort.
Rooms: a bit cramped, but fairly quiet and kept reasonably clean.
People: great crowd of backpackers, exchange students, and wanderers. As well as plenty of Americans, there are also quite a few Brazilians staying here (as the owner is Brazilian).
Staff: friendly, laid-back, English-speaking, and willing to introduce you to the place and to Rome.
Location: quick walk from Termini, the central train station. Also reasonably close to various attactions, such as the Colisseum.
Food: free breakfast is basic but good — cereal, toast, juice, and tea/coffee. The kitchen is also great — you can cook dinner here at any time, which will save a few bucks when in Rome.
Internet: 1 free PC, which is very popular — handy little extra, but you'll have to win a gladiatorial fight-to-the-death just for 5 minutes on it.
Hot water: not particularly reliable — in my experience, it's of limited heat in the morning, and it's stone cold at night.