In their FB post the rally commitee indicated more rooms have opened up:

More Hotels and Condos have opened up at Sunday River. Call now to make your reservations for the Northeast Regional Rally.

Maine Ski Lodging Company-On Sunday River Property
16 Parkway
Bethel Maine
207-824-4000
Rates: $89-$119 per night
Promo Code HOG on website or when calling
http://www.maineskilodging.com/

Mountain Village Lodge
134 Mayville Road
Bethel, ME 04217
207-824-4000
Rates: $109-$139 per night
Promo Code HOG on website or when calling
www.mountainvillagelodge.com

River View Resort
357 Mayville Rd, Bethel, ME
207-517-9412
Rates: $129 per night
www.riverviewresort.com

Sudbury Inn
151 Main St, Bethel, ME 04217
207-824-2174
Rates: $89-$159 per night
http://www.thesudburyinn.com/

The Victoria Inn
32 Main St, Bethel, ME 04217
207-824-8260
Rates: $119-$149 per night
http://www.thevictoria-inn.com/

Pleasant River Motel
764 W Bethel Rd, W Bethel, ME 04286
Rates: $70 per night
207-836-3575
http://pleasantrivermotel.net/index.html

Chapman Inn
1 Mill Hill Road, Bethel ME 04217 (207) 824-2657
Rates Single (Bunk style) $35.00
Room Weekday $89- $109.00 Room Weekend $119.00