http://www.wordreference.com/
The word reference is a trustworthy dictionary for French, Italian, Spanish, and English. It provides definitions from multiple countries.
English to French, Italian, German & Spanish Dictionary - WordReference.com. Word Reference. Web. 07 Nov. 2011.
Wikipedia.org http://www.wikipedia.org/
Wikipedia is probably the most trusted contemporary encyclopedia. It has search engines for twelve different languages including Spanish. It is under constant revision by it's myriad world wide members.
General resources
Dictionary.com
http://spanish.dictionary.com/?__utma=1.363396502.1320703724.1320703724.1320703902.2&__utmb=1.1.10.1320703902&__utmc=1&__utmx=-&__utmz=1.1320703902.2.2.utmcsr=google%7Cutmccn=(organic)%7Cutmcmd=organic%7Cutmctr=www.dictionary.com%2F&__utmv=-&__utmk=2070065This Spanish dictionary offers a very similar service as Reference Dictionary. It offers meanings from different Spanish-speaking countries and regions.
WordReference.com
http://www.wordreference.com/The word reference is a trustworthy dictionary for French, Italian, Spanish, and English. It provides definitions from multiple countries.
English to French, Italian, German & Spanish Dictionary - WordReference.com. Word Reference. Web. 07 Nov. 2011.
Wikipedia.org
http://www.wikipedia.org/
Wikipedia is probably the most trusted contemporary encyclopedia. It has search engines for twelve different languages including Spanish. It is under constant revision by it's myriad world wide members.