http://noticias.juridicas.com/base_datos/
This database contains a large number of Spanish law texts, including several codigos. It is free of charge and in Spanish only.

http://constitucion.rediris.es/CodigoConst/Codigo.html
Another collection of Spanish law texts. Again in Spanish and free of charge.

http://www.lexadin.nl/wlg/legis/nofr/eur/lxwespa.htm
A database of Spanish law texts, provided by Lexadin. It offers a broad number of Spanish law texts including commercial, civil and administrative law. The entire website as well as the texts themselves are being offered in Spanish only, free of charge.

http://www.tribunalconstitucional.es/mapa/mapaweb.html
This page provides an overview of the content of the official page of the constitutional court of Spain. It contains the Spanish constitution for free in several translations, including English and German. It also provides a number of decisions by the court in full text and in Spanish, from the year 2000 on.

http://www.poderjudicial.es
This page contains basically a portal for everything concerning Spanish law. Following the linked images on the first page, one reaches a page containing a link called "jurisprudencia", which again opens a menu on the left hand side providing a search mask for decisions of Spain's major courts.