Hotel development is coming back to life in Boston.

After a two-year drought in which no new hotels opened, six are set to begin operations over the next two years, from the modern 480-bed hostel that launched last month to a 210-room Courtyard by Marriott near TD Garden slated to open in 2014. Between these properties and 17 other proposed hotel projects, Boston could potentially add more than 4,000 hotel rooms, an expansion that could attract more conventions and rein in climbing room rates.