OK, so you're not camping, but for others attracted by the post title----
Two of us are cycle camping Santiago de Compostela to Lisbon through the more remoter areas in 2 weeks time and primarily got our sites from this link here
(scroll the map into Spain and the campsites come into view).
Google maps is also helpful e.g. search on town-name
and then enter search criteria camping near town-name
. This is not a fool-proof method but between the two you'll cover many of the available sites.
The ACSI site can also be helpful here
I like camping over B&B for the variety of people you meet but there is the kit aspect of course - each to their own eh