Try buying books that you are already familiar with in English, or that you already enjoy. This will make it both easier to understand in Spanish and more enjoyable for you to read. Search Amazon for “[title of my favorite book] spanish” or “[title] espanol”. Many of the classics and current popular books are available in Spanish, such as The Secret Garden, Pride and Prejudice, The Chronicles of Narnia, Harry Potter, Game of Thrones, and The Hunger Games.
One series that I like are the Penguin parallel Spanish texts. These and books like them are called “bilingual” or “bilingüe” or “dual text” or “parallel text”, because they have English right along side the Spanish on the facing page.
For beginner books, try searching “spanish reader”.
2. Your local library
My library has a search engine on its website that allows you to narrow down materials by type and language. You can also check the Spanish stacks at different branches. In my library, the children’s and young adult books are on different stacks than the adult literature. Of special interest are books that have SPA and ENG on the spine, because these are bilingual / dual-language books.
I’ve found that many children’s books have both the Spanish and the English in them. Beware though, I have also found that even the children’s books can be difficult because of their use of a variety of grammar tenses and obscure vocabulary.
3. Online educational websites
Aula de lengua — this website has lessons for beginner, intermediate, and advanced learners, with Flash-based activities and cultural notes to use before and after reading the text. The beginner section is pretty difficult for absolute beginners but should be manageable after you’ve learned a few hundred words.
OnlineSpanish – here’s a few texts ordered by proficiency with the language. The beginner texts truly are readable by beginners and are much shorter than the advanced texts.
Lonweb Parallel Texts – here you’ll find a few stories with the English and Spanish side by side. Just scroll down and look on the left hand side under the Spanish header for more stories.
International Children’s Digital Library — this is an archive of over 100+ Spanish children’s books, complete with illustrations. On the left, click Read Books, then select the Spanish language.
Many Wikipedia articles have volunteer submitted translations in Spanish — just look at the languages on the left hand side of the article. Looking up translations in Wikipedia of articles in your interest area is a great way to learn jargon and technical terminology, or words that you can’t find in the dictionary. These articles tend to be pretty difficult and I would only recommend this for advanced students. It’s a good way to get properly translated sentences though.
Wikisource also has Spanish texts without translations, including historical and religious documents, essays, short stories, fables, and more. These are also very difficult. You can find spoken audio renditions of many of these texts on LibriVox.
Vikidia is a wikipedia for kids and young people using easy to understand Spanish. It’s a great place to look for texts to read for advanced beginner and intermediate.
5. Other websites
BBC Mundo – The news in Spanish. On the one hand this is difficult to read, but on the other hand your familiarity with current events will facilitate your understanding.
El País – Another Spanish newspaper.
Menéame – The Spanish reddit. Articles are upvoted based on popularity.