Business Spanish
Two free new lessons a day on business conversational Spanish.

Cuban Idioms
Idioms and colloquialisms specific to Cuban Spanish. The author calls it Cubonics. [English/Espaņol]

Conjugation Trainer
Tutorial on the verb conjugations. It provides an interactive page to test you on selected verbs. [English/Deutsch]

Dichos Boricuas
Common saying in Puerto Rico. You'll notice the words are often broken with apostrophes to indicate the unique Puerto Rican way of speaking Spanish. [Espaņol]

Learn Spanish
Verb drills, cultural notes, and an idiom generator. This is a very extensive online tutorial which eventually offers a more detailed course for a cost.

Spanish at About.com
Go to this expert site on the subject of the Spanish language.

Spanish Pronto
Vocabulary, the basics, reading practices, and tools (links and suggestions) for Spanish study and reference.

Vox dictionary
Provides English dictionary definitions for Spanish words you provide.

Web Spanish Lessons
Lessons on Mexican Spanish. They have a section to test yourself on translating both languages.