In late Nov 2010, I stayed 2 nights at a wonderful little guesthouse near the Luang Prabang P.O., the Souksavath GH - Houaxieng Village N; 16/01, phone (856-71) 212043
This place is tiny with 5 rooms, but very comfy and friendly as well as clean. I paid $12. for my wood paneled room with ensuite bath. A great 2nd floor balcony with hanging orchids was right in front. This street of mainly backpacker places is right behind JOMA Bakery on the main drag of LP. I just wish I had stayed longer at the Souksavath - super friendly manager here. Free guest computer in the lobby, no breakfast (the bakery is a 1 minute walk from here - nice food).