This site allows you to see detailed information on the top 60,000 words (lemmas) of English, based on data from the Corpus of Contemporary American English (COCA).
You can see the overall frequency for each word, as well as the frequency of words in different kinds of English -- spoken, fiction, magazines, newspapers, and academic writing. For each word you can also find the 20-30 most frequent collocates (nearby words) and see 200 or more concordance lines (words in context). You can also see a list of synonyms and (from WordNet) words with more specific and more general meanings, and in all of these cases you can click to see the entries for those related words as well.
If this is your first time here, you'll probably want to spend 1-2 minutes looking at the Guided Tour, or just search for a random word or random frequency range to get started. If you've used COCA before, you might want to look at the comparison of the two resources. You might also want to consider downloading the data for offline use.