Diccionarios
Word Reference - This resource will not translate entire sentences. Click on "Verb Conjugators" to see different verb forms and "Language Forums" for help with phrases.
Larousse - One of the best dictionaries available, including audio pronunciation guides. Search for words in Spanish, French, German and Italian.
Spanish Dictionary.com - This is a basic online dictionary that will also conjugate verbs. It is also available as an app for iPhone and Android. The app offers games and a "word of the day" activity.
Diccionarios.com - Este diccionario define las palabras en español—un recurso excelente para hispanoparlantes.
Diccionario de sinónimos - Online thesaurus.
Diccionario de sinónimos y antónimos – Online thesaurus.
Diccionario de modismos y expresiones idiomáticas – Look up idioms in this useful dictionary.