Hostel Clan, BA
My mate Patrick recommended Clan to me, back in Ecuador. It's one of the several big party hostels here in Buenos Aires (a city that is one big party, all night every night), and although the building is a bit of a dump, it's very friendly and it has a lot of character. The upstairs bar is the place to hang out every night, and it also has a ping-pong table and a TV, for keeping yourself entertained during the day. The hostel has free bikes, that you can borrow for riding around the city at any time. They arrange weekly games of fútbol ("soccer"), as well as twice- or thrice-weekly trips to see teams such as the Boca Juniors playing at the big fútbol stadium. They do all-you-can-eat BBQs a few nights a week. And they'll even hire buses to take you to the big discos in town, on Friday and Saturday nights. Just don't expect to get any sleep here, before about 4am each morning.
Rooms: a bit dilapidated (creaky floors, broken window-shutters, etc), and a bit cramped and dirty. But the beds do the job. And you don't come here to sleep, anyway.
People: what I've come to recognise as "the Loki crowd" — i.e. mainly English-Irish-Scottish folk, and mainly big drinkers and big party-goers. All very warm, and all there to meet fellow travellers. Many are also in town for a while.
Staff: predominantly porteños (i.e. BA locals), although most speak good English. All hospitable and informative, and most will come up to the bar for a drink in the evening (or just get drunk downstairs, while on duty at the reception desk :P).
Location: downtown, near all the other backpacker joints — one block from Av 9 de Julio, which is the main drag through the city. Also conveniently close to a subte (subway) station.
Food: wholesome all-you-can-eat breakfast of cereal / milk, bread (w/ butter, jam, and dulce de leche), bananas, oranges, fruit juice, and tea / coffee. The kitchen (also a bit dilapidated, but adequate) is available for guests to cook in, 24/7.
Internet: 3 PCs, which are always very busy, and which all share a highly unreliable network connection. The PCs themselves are also some of the buggiest I've ever used in my life: one of them is "epileptic" (seriously — it goes psycho every 5 minutes or so, starts randomly opening programs, racing the mouse around the screen, etc). But OK for a quick e-mail check. Plus: for laptop owners, the Clan B&B, across the road, has Wi-Fi available, which Hostel Clan guests can also use.
Hot water: reliable and high-pressure, although the bathrooms (like the rest of the hostel's facilities) are not the nicest or the cleanest I've ever seen.