The dictionary of choice by Gabriel García Márquez:"Moliner wrote, with her bare hands, the most complete, most useful, most diligent and most amusing dictionary of the Castilian language".
"The dictionary includes words that are native to the Americas as well as those that originated in Spain but whose meaning has been modified. It also lists words that although no longer used in Spain, are kept alive in the different varieties of Latin American Spanish. Over 70,000 words, complex lexemes and phrases; over 120,000 meanings communication and lexicalization * Sociolinguistic distinctions (socio-economic level, linguistic style, social value) for each meaning
By Real Academia Espanola. Guides users throughout the proper use of the Spanish language. It is a work conceived from all the Hispanic countries, which maintains a fundamental balance between the variety of a languages spoken in so many different regions, and the linguistic unity that must be preserved. It includes: Most frequently used words from other languages; Solutions to very diverse grammatical problems; Information on the rules of accentuation; Models of verbal conjugations; and more.
Gramáticas
El buen uso del español by Real Academia Española
Una gramática académica que refleja todas las variedades del español, el resultado de once años de intenso trabajo de las veintidós Academias de la Lengua Española. Un mapa de la unidad y variedad del español, una obra práctica que, uniendo tradición y modernidad, fija la norma para todos los hispanohablantes. De Buenos Aires a La Habana, de México a Medellín, de Los Ángeles a Madrid.
Dictionary of the Spanish Language of the Royal Spanish Academy (DRAE) is an all Spanish dictionary, published by the Royal Spanish Academy, the official institution for regulating the Spanish language.
Takes definitions from the Webster's New World Concise Spanish Dictionary, and offers a phrasebook and answers forum alongside traditional entries. The dictionary also has optional features such as flashcards and a word of the day email newsletter.
Helpful online tool for conjugating Spanish verbs. Type in the infinitive form of the verb to instantly see conjugations in either table or list format. Also has an option to show or hide pronouns as well as conjugate only certain tenses. Features a very simple and easy to use interface.
Offers two free dictionaries, the Concise Oxford Spanish Dictionary (2005) and the Diccionano Espasa Concise (2000). The Oxford dictionary features several support features and mechanisms for finding related entries in both Spanish and English.