Google Translate is a good place to translate a few words or a paragraph:
Need a quick place to translate a few words:
http://www.merriam-webster.com/dictionary/Spanish
A great place to find everything ESL:
This site lists the grammar rules of English alphabetically, and they are easily accessible:
There are hundreds of idioms listed on this site as well as phrasal verbs and other grammatical irregularities that you may need help with: