Absolute Paris Hostel is a pretty good bet -- located in a pretty good part of Paris and there's no curfew or lockout!
The hostel is located in the Republique area of the 11th arrondissement just across from the end of the Canal St. Martin. To get to the hostel take the metro line 3, 5, 8, 9, or 11 and follow the Sortie sign for rue du Faubourg du Temple and when you are above ground start walking away from the statue in the middle of the traffic circle. You will walk down rue du Faubourg du Temple and the hostel will be on the corner of the fourth street on your right, rue de la Fontaine au Roi. This will be right after you have crossed the Canal St. Martin. It is across the street from a McDonald's on one side and a Franprix on the other.
Rooms and Bathrooms
The rooms open with a card, but as far as the room we stayed in went, no one's card ever worked. Someone always has to come and open the door to let everyone else in. The people at the desk are no help in resolving the broken card problem. The room itself is clean if nothing else -- it seems to be an old hotel room turned into a dorm to sleep four people on two sets of bunk beds. The beds are made of metal and creak incessantly when people move in their sleep. Also, there are no ladders to the top bunk. The bunks are too close together for someone to be able to comfortable sit up on the bottom bunk without hitting their head.
Otherwise, the room is rather dim without the curtains open and there is no light besides the one overhead to use when coming home in the middle of the night. The cleaning staff will come in at an ungodly hour to make the beds and if you intend to sleep in after a long night out they will probably wake you up (around 10 a.m.). There are no lockers but there is a small closet with one safe to lock valuables in. The telephone and a television in the room does not work.
The bathrooms are ensuite and consist of the basic sink, toilet, and shower cubicle that gets water all over the floor despite the curtain. There really is nowhere in the bathroom to set clean clothes to keep them dry while showering. There is a soap dish in the shower as well as a small shelf above the sink for placing toiletries. The bathroom, and especially the shower cubicle itself, is small and doesn't leave much room for moving around. Towels and a hair dryer, as well as a bar of soap and shampoo packets, are provided. The bathroom is also home to the only trash can in the room.
The atmosphere of this hostel is probably best described as subdued but friendly. Guests don't seem to socialize outside their travel group (we were in a room of single travelers, so we talked to each other). The lobby of the hostel is the main common area besides the breakfast room. In the lobby there are three computers with free internet access for guests (limited to twenty minutes when someone is waiting, and you will have to remind the person using the computer of the rule if you ever want to use it). There is also free Wi-Fi.
There is a coffee machine and vending machine in the lobby as well as tourist information and a television that seems to be there more for the entertainment of whoever is working the front desk than for the backpackers. There is no luggage storage room per se but you can leave bags next to the check-in desk in the hall for the afternoon. There is nothing to secure a bag to, but there are video cameras watching them (but who's watching the cameras?). Breakfast comes free with your bed and is strictly handed out -- one glass of orange juice, one glass of something hot (coffee, tea, hot chocolate), and croissant, and one roll with optional jelly and butter. Breakfast is served in the basement breakfast room until 9:30.
This hostel seems fine -- overall it is clean and it's one of the few hostels within the city limits of Paris with twenty-four-hour check-in and no curfew and no lockout. Check-out is at 11 a.m. It isn't the most social hostel but it's a good place to stay if you're day will be full and you already have friends to hang out with. You have to go outside to smoke. The front desk staff seems much nicer if you at least try to speak to them in French -- don't expect everyone at this hostel to be capable of speaking English. If a booking website says all the beds are full, try calling or sending an e-mail, because they keep some other beds open. If you come in late at night be prepared to give your name and room number to the person working the desk. There is an elevator.