Dictionaries and their online counterparts can give you the straight-up meaning, and maybe sentence context, of a word you're fuzzy on. The Wordnik site wants to show you all the conversations, pictures and other talk about your word.
Not that Wordnik doesn't give you multiple dictionary definitions, etymologies, and even pronunciation sound files for your look-ups. Its value service, however, is the extra context provided by highlighted Twitter posts, Flickr photos, related tags and other multimedia on the results page. It's all spread out on a single multi-column page, but you can hit the sub-menus near the top to get a full page of any of them. Statistic geeks can also see how often words are being used online and the number of look-ups on Wordnik for a word. The site could be helpful for when you've got to get up to speed on something quickly and get a bit deeper than just a brief explainer.
Wordnik is free to use; signing up and logging in lets you track select words and history.