HI-Boston sets the standard for urban hostels, with its modern, ecofriendly facility in the historic Dill Building. Purpose-built rooms are functional and clean, as are the shared bathrooms. Community spaces are numerous, from fully equipped kitchen to ground-floor cafe, and there's a whole calendar of activities on offer. The place is large, but it books out, so reserve in advance.
Dorms vary in size and with guest gender; prices vary accordingly.