I would recommend staying at Samosir Cottages located on the Tuk Tuk area of Samosir Island. The rooms are very clean and comfortable and prices range from Rp 25,000 to 75,000 (about $2.50-$7.50 USD) a night with hot water, western toilets, some even have bath tubs and satellite televisions. There is a restaurant on site and internet access is available. In the evenings you can enjoy traditional Batak music and dancing.