Graus expertizing - Very nice site with alot of detailed images of genuine stamps for comparing.
Spanish-Philippine stamps - Nigel Goodings excellent site.
Soler y Llach - International auctions.
Edifil catalogs - Edifil's official website.
Free downloadable album pages - From Francisco Luzón Martínez.
filateliadigital.com - Some interesting articles here on Spanish stamps
If you have a webpage that would fit in here let me know and I will add it on. Or, if you have ssen any interesting Spanish stamp collecting sites give me a holler at: email@example.com and I'll add it as well.