Platiquemos means Let's Talk
Learn to speak Spanish like a diplomat

 
  About.com is a site that provides information about almost anything you can think of.  For each category, the site has a "guide".  The "guide" for the Spanish language section is Gerald Erichsen who has been doing a great job for years.  The site offers articles about aspects of the Spanish language and a message board for Spanish learners.  Highly recommended as a supplementary to Spanish learning, either in classes or on your own.

  ¿Le gustan chistes?  Like jokes? En este sitio hay un 
  nuevo chiste cada día, en español.  This is a site that
  has a new joke in Spanish every day.  You can sign up
  to have a joke delivered to your e-mail every day.  Jokes, like music, can be valuable aids to language learning. 

Spanish - English and English - Spanish dictionaries

     Online:  About the best one I've found is

     Another decent one is here.

     Downloadable: 

     Downloadable pocket dictionaries from Microsoft website.

A site that offers a multitude of links to almost anything you can think of about the Spanish language and the Latin culture, as well as many other languages and cultures.  This site is maintained by Eva Easton, and is used a great deal by language teachers as a resource.

A site that offers slang (jerga) and colloquialisms (modismos) from different Spanish-speaking countries.  The site is all in Spanish, so will be most useful to advanced students.  Even advanced students are cautioned, however, that while many of the words and expressions you'll find here are harmless, some need to be used with care only by those who are entirely comfortable with both the culture and the people they're talking to.  In general, slang should be part of your "passive" vocabulary (you understand it), but caution should be exercised in incorporating it into your "active" vocabulary (you say it).  A good way to pick up some of the words that are peculiar to different countries you might be visiting.

  You can get the conjugation for any Spanish verb at this
   site.  Sometimes it's almost too much: plusquamperfecto is one of the tenses conjugated.  Also has other information about the Spanish language.