There are several dictionaries available on the internet.  There are ones created by users.  There are visual dictionaries and there are just dictionaries of pronunciation.  But Word Ahead has built up an impressive amount of videos explaining words and providing rich visuals too.  They currently have over 515 videos of words to choose from.  Most of the words are extremely difficult words that are found on standardized college-entry tests.  This is a great resource for English language learners or high school students preparing for college in the states.  You can even upload your own videos to the library.  Also note that they have a widget available that can be embedded into any blog articles.  And it's all free!