TopRural offers a very complete list of rural accommodations (houses, bed and breakfasts, hotels, ...) in Spain including detailed information, travellers’ opinions and pictures.

From the introduction: "TopRural is a private and independent company, whose aim is to promote rural tourism . With this objective, TopRural is working to offer the traveller the best information available to organize their rural escapes, and the owner the most profitable way of promoting their accommodation. "

The Web site is very clear and seems to be frequently updated.