The three closest hotels are:
The Charles Hotel (walking distance)
One Bennett Street, Cambridge, MA 02138
617-864-1200
617-864-5715
Harvard Square Hotel (walking distance)
110 Mt. Auburn Street, Cambridge, MA, 2138
617-864-5200
617-864-2409
Sheraton Commander Hotel (closest to the conference)
16 Garden Street, Cambridge, MA 02138
Main: 617-547-4800
Fax: 617-868-8322
Reservations: 800-535-5007
email: sales@sheratoncommander.com
More Harvard University Area Hotels
Airbnb is another good option. There are lots of cost effective accommodations available.