Hotel Gaylord - 150Rps for a single room with shared bathroom. Perhaps the cheapest central option in the city center.
Hotel Yaisana - Brand new hotel as of March 2012. Single rooms from 300Rps shared bathroom update [June 2015]: still under construction, price for smelly double room with bathroom, fan, but without window haggled down to 1000Rps; quite noisy, room quality varying, so check more of them
Not far from Hotel Yaisana: Hotel Nongin, 9774269422, 0385-2440596, big double room with bathroom, fan, windows and balcony for 1000Rps [June2015]
Hotel Mayur, Old Assembly Rd: cheap budget option, really run down, shared bathroom, windows in some rooms, mosquito net; double for 460Rps [June 2015]
Also, in MG Avenue you can find Hotel Nirmala single around rs. 600, double 1200, White Palace, Hotel City Heart and Hotel Avenue all pretty close by. Single rooms from 300-400Rps.
In the bus Stop/stand area of B.O.C area, there is Hotel Imphal, which is run by the manipur tourism department. It is cheap, well maintained and have a spacious garden.
Classic Hotel, which is located close to the bus stand in B.O.C area is the best hotel in Imphal yet. It is new, clean, well maintained and helpful staff and with a fine dining restaurant. It is close to the city center and located just opposite to the historical Kangla fort.
Hotel Excellency in the airport road, Hotel Anand Continental in the Thangal Bazar and Hotel Bheigo in Keishampat area, are other cheap to moderately price hotels in Imphal.