The best Spanish dictionary on the net is..

At the beginning of this list we must place spanishdict.com . It certainly is one of the leading internet dictionaries and that's because of it's huge database, it's in depth translations covering regional variations and audio pronunciations.
It's quite easy to use the spanish dictionary at spanishdict.com, you just type your word and press enter and you will be presented with the translation. It's not just words which can be translated, you can also have sentence translated to and from spanish or english both ways, and that service is made available through Google, FreeTranslation and BabelFish services. All of these are offcourse Machine Translation tools. Besides dictionary, there is also an active forum where you can communicate with many native Spanish/English speakers and ask something if you need to. And on top of all this, you can also join classes on the site if you wish to learn spanish. All in all an excellent resource.
At my-spanish-dictionary.com there is an interesting creation. Most of the sites on the net are created more less similar but this is something different. Although simple, it is still awesome idea of combining pictures and their corresponding words in English and Spanish. What makes it better is that it brings your attention into focus where learning is easier. Looking at the picture you may memorize words connected to that picture and so visual learning is probably one of the best ways to learn new language, Spanish or any other, so be sure to take a look.
A team at the University of California created Spanish Dictionary of Agriculture & HR Management with intention to help farm employers learn Spanish in order to better communicate with their Spanish-speaking workers with the basis on the audio part of learning.
Creators say that the neutral version of Spanish is used wherever possible, and so when they had to decide between multiple correct Spanish words that exist for an English one the preference would be given to the word spoken in Mexico. Spanish Language Audio files consist of generally spoken words and of course Agriculture related vocabulary. Files come in mp3 format which is the most popular music format which means that this format is also videly supported on all kinds of audio players. You can listen to pronounciation of Spanish alphabet, have practice with vowels, learn Greetings and Expressions, learn how to say days, numbers, holidays, how to give driving directions and instructions, learn about animal's and plant's names and a whole lot of other things. And of course there is a written English Spanish dictionary available. So, an excellent resource.
When speaking foreign language or any language for that matter, one word is almost never enough to describe something. The trouble may arise when we try to apply our way of thinking and our way of building sentences into another language. Sometimes it works, but sometimes it isn't. Well, then resources like v7w.com's English-Spanish and Spanish-English Dictionary and Text Composition System really come in handy. Beside dictionary there is also a nice list of commonly used text patterns, Correspondence, Contracts and Scientific abstracts. It is quite a valuable resource for anyone who had tried to comprehend or write some response in any language, in this case Spanish.